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<h3><a name="t0" target="_blank"></a> 10.1.1 創建存儲過程</h3>
<p> 存儲過程就是一條或者多條SQL語句的集合，可以視爲批文件。它可以定義批量插入的語句，也可以定義一個接收不同條件的SQL。</p>
<p> 創建存儲過程的語句爲 CREATE PROCEDURE，創建存儲函數的語句爲CREATE FUNCTION。</p>
<p> 調用存儲過程的語句爲CALL。</p>
<p> 調用存儲函數的形式就像調用MySQL內部函數一樣。 </p>
<pre class="has" name="code"><code class="hljs sql"><ol class="hljs-ln"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">DROP</span> <span class="hljs-keyword">TABLE</span> <span class="hljs-keyword">IF</span> <span class="hljs-keyword">EXISTS</span> t_student;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> </div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="3"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">TABLE</span> t_student</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="4"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">(</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="5"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">id</span> <span class="hljs-built_in">INT</span>(<span class="hljs-number">11</span>) PRIMARY <span class="hljs-keyword">KEY</span> AUTO_INCREMENT,</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="6"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">name</span> <span class="hljs-built_in">VARCHAR</span>(<span class="hljs-number">255</span>) <span class="hljs-keyword">NOT</span> <span class="hljs-literal">NULL</span>,</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="7"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> age <span class="hljs-built_in">INT</span>(<span class="hljs-number">11</span>) <span class="hljs-keyword">NOT</span> <span class="hljs-literal">NULL</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="8"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="9"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> </div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="10"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">INSERT</span> <span class="hljs-keyword">INTO</span> t_student <span class="hljs-keyword">VALUES</span>(<span class="hljs-literal">NULL</span>,<span class="hljs-string">'大宇'</span>,<span class="hljs-number">22</span>),(<span class="hljs-literal">NULL</span>,<span class="hljs-string">'小宇'</span>,<span class="hljs-number">20</span>);</div></div></li></ol></code><div class="hljs-button {2}" data-title="複製" onclick="hljs.copyCode(event)"></div></pre>
<p> <img alt="" class="has" height="64" src="https://img-blog.csdnimg.cn/20181103135041603.png" width="198"></p>
<p> 如上述，t_student表中的數據有兩條。如果我們要分別查詢出來這兩條數據，顯然就是根據ID來查詢。查詢出來了第一條數據以後，我們可能會去做其它的操作。等過兩天，我們要查詢另外一條記錄的時候，可能又要再寫一次這樣的查詢語句。</p>
<p> 如果能像Java那樣，提供一個ID，就能查詢到指定ID的記錄，這樣就可以複用之前寫的SQL語句。對於查詢SQL語句，我們能不能像Java那樣，封裝這個查詢學生的SQL呢？存儲過程與存儲函數應運而生。</p>
<p> 定義一個根據ID查詢學生記錄的存儲過程。</p>
<pre class="has" name="code"><code class="hljs sql"><ol class="hljs-ln"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">DROP</span> <span class="hljs-keyword">PROCEDURE</span> <span class="hljs-keyword">IF</span> <span class="hljs-keyword">EXISTS</span> getStuById;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> </div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="3"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">DELIMITER // <span class="hljs-comment">-- 定義存儲過程結束符號爲//</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="4"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">PROCEDURE</span> getStuById(<span class="hljs-keyword">IN</span> stuId <span class="hljs-built_in">INT</span>(<span class="hljs-number">11</span>),<span class="hljs-keyword">OUT</span> stuName <span class="hljs-built_in">VARCHAR</span>(<span class="hljs-number">255</span>),<span class="hljs-keyword">OUT</span> stuAge <span class="hljs-built_in">INT</span>(<span class="hljs-number">11</span>)) <span class="hljs-comment">-- 定義輸入與輸出參數</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="5"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">COMMENT</span> <span class="hljs-string">'query students by their id'</span> <span class="hljs-comment">-- 提示信息</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="6"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">SQL</span> <span class="hljs-keyword">SECURITY</span> DEFINER <span class="hljs-comment">-- DEFINER指明只有定義此SQL的人才能執行，MySQL默認也是這個</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="7"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">BEGIN</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="8"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">SELECT</span> <span class="hljs-keyword">name</span> ,age <span class="hljs-keyword">INTO</span> stuName , stuAge <span class="hljs-keyword">FROM</span> t_student <span class="hljs-keyword">WHERE</span> <span class="hljs-keyword">id</span> = stuId; <span class="hljs-comment">-- 分號要加</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="9"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">END</span> // <span class="hljs-comment">-- 結束符要加</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="10"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">DELIMITER ; <span class="hljs-comment">-- 重新定義存儲過程結束符爲分號</span></div></div></li></ol></code><div class="hljs-button {2}" data-title="複製" onclick="hljs.copyCode(event)"></div></pre>
<blockquote>
<p>語法： CREATE PROCEDURE sp_name(定義輸入輸出參數) [ 存儲特性 ] BEGIN SQL語句； END</p>
<p>IN 表示輸入參數，OUT表示輸出參數，INOUT表示既可以輸入也可以輸出的參數。sp_name爲存儲過程的名字。</p>
<p>如果此存儲過程沒有任何輸入輸出，其實就沒什麼意義了，但是sp_name()的括號不能省略。</p>
</blockquote>
<p> 查看剛纔創建的存儲過程。</p>
<pre class="has" name="code"><code class="hljs delphi">SHOW <span class="hljs-function"><span class="hljs-keyword">PROCEDURE</span> <span class="hljs-title">STATUS</span> <span class="hljs-title">LIKE</span> '<span class="hljs-title">g</span>%'</span></code><div class="hljs-button {2}" data-title="複製" onclick="hljs.copyCode(event)"></div></pre>
<p> <img alt="" class="has" height="81" src="https://img-blog.csdnimg.cn/20181103142229130.png" width="891"></p>
<p> 下面是調用存儲過程。對於存儲過程提供的臨時變量而言，MySQL規定要加上@開頭。</p>
<pre class="has" name="code"><code class="hljs css"><ol class="hljs-ln"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-selector-id">#study</span> 是當前數據庫名稱</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> </div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="3"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-selector-tag">CALL</span> <span class="hljs-selector-tag">study</span><span class="hljs-selector-class">.getStuById</span>(1,@<span class="hljs-keyword">name</span>,@<span class="hljs-keyword">age</span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="4"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> </div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="5"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-selector-tag">SELECT</span> @<span class="hljs-keyword">name</span> AS stuName,@age AS stuAge;</div></div></li></ol></code><div class="hljs-button {2}" data-title="複製" onclick="hljs.copyCode(event)"></div></pre>
<p> <img alt="" class="has" height="71" src="https://img-blog.csdnimg.cn/20181103140519116.png" width="220"></p>
<pre class="has" name="code"><code class="hljs sql"><ol class="hljs-ln"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">CALL</span> getStuById(<span class="hljs-number">2</span>,@<span class="hljs-keyword">name</span>,@age);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> </div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="3"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">SELECT</span> @<span class="hljs-keyword">name</span> <span class="hljs-keyword">AS</span> stuName,@age <span class="hljs-keyword">AS</span> stuAge;</div></div></li></ol></code><div class="hljs-button {2}" data-title="複製" onclick="hljs.copyCode(event)"></div></pre>
<p> <img alt="" class="has" height="81" src="https://img-blog.csdnimg.cn/20181103140542642.png" width="220"></p>
<p> 這樣做的好處是，如果一段較爲複雜的SQL語句，我們可能過了幾天再去寫它，又費事又費力。存儲過程可以封裝我們寫過的SQL，在下次需要調用它的時候，直接提供參數並指明查詢結果輸出到哪些變量中即可。</p>
<blockquote>
<p>提示：如果存儲過程一次查詢出兩個記錄，將會提示出錯。[Err] 1172 - Result consisted of more than one row</p>
<p> 所以需要在存儲過程的SQL後面加上LIMIT 1。從位偏移量爲0的，即從查詢結果的第一條數據開始，查詢一條記錄。</p>
</blockquote>
<h3><a name="t1" target="_blank"></a>10.1.2 創建存儲函數</h3>
<p> 存儲函數與存儲過程本質上是一樣的，都是封裝一系列SQL語句，簡化調用。</p>
<p> 我們自己編寫的存儲函數可以像MySQL函數那樣自由的被調用。</p>
<pre class="has" name="code"><code class="hljs sql"><ol class="hljs-ln"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">DROP</span> <span class="hljs-keyword">FUNCTION</span> <span class="hljs-keyword">IF</span> <span class="hljs-keyword">EXISTS</span> getStuNameById;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> </div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="3"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">DELIMITER //</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="4"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">FUNCTION</span> getStuNameById(stuId <span class="hljs-built_in">INT</span>) <span class="hljs-comment">-- 默認是IN，但是不能寫上去。stuId視爲輸入的臨時變量</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="5"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">RETURNS</span> <span class="hljs-built_in">VARCHAR</span>(<span class="hljs-number">255</span>) <span class="hljs-comment">-- 指明返回值類型</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="6"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">RETURN</span> (<span class="hljs-keyword">SELECT</span> <span class="hljs-keyword">name</span> <span class="hljs-keyword">FROM</span> t_student <span class="hljs-keyword">WHERE</span> <span class="hljs-keyword">id</span> = stuId); // <span class="hljs-comment">-- 指明SQL語句,並使用結束標記。注意分號位置</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="7"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">DELIMITER ;</div></div></li></ol></code><div class="hljs-button {2}" data-title="複製" onclick="hljs.copyCode(event)"></div></pre>
<p> 使用存儲函數。</p>
<pre class="has" name="code"><code class="hljs sql"><span class="hljs-keyword">SELECT</span> getStuNameById(<span class="hljs-number">1</span>);</code><div class="hljs-button {2}" data-title="複製" onclick="hljs.copyCode(event)"></div></pre>
<p> <img alt="" class="has" height="67" src="https://img-blog.csdnimg.cn/20181103143613991.png" width="196"></p>
<blockquote>
<p>提示：在RETURN 語句後面，有趣的是，分號在SQL語句的外面。如果不加分號，查詢結果居然查詢出兩條記錄，很奇怪。</p>
</blockquote>
<p> 從上述存儲函數的寫法上來看，存儲函數有一定的缺點。首先與存儲過程一樣，只能返回一條結果記錄。另外就是存儲函數只能指明一列數據作爲結果，而存儲過程能夠指明多列數據作爲結果。</p>
<h3><a name="t2" target="_blank"></a>10.1.3 定義變量</h3>
<p> 如果希望MySQL執行批量插入的操作，那麼至少要有一個計數器來計算當前插入的是第幾次。 </p>
<p> 這裏的變量是用在存儲過程中的SQL語句中的，變量的作用範圍在BEGIN .... END 中。</p>
<p> 沒有DEFAULT子句，初始值爲NULL。</p>
<p> 定義變量的操作</p>
<pre class="has" name="code"><code class="hljs sql"><ol class="hljs-ln"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">DECLARE</span> <span class="hljs-keyword">name</span>,address <span class="hljs-built_in">VARCHAR</span>; <span class="hljs-comment">-- 發現了嗎，SQL中一般都喜歡先定義變量再定義類型，與Java是相反的。</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">DECLARE</span> age <span class="hljs-built_in">INT</span> <span class="hljs-keyword">DEFAULT</span> <span class="hljs-number">20</span>; <span class="hljs-comment">-- 指定默認值。若沒有DEFAULT子句，初始值爲NULL。</span></div></div></li></ol></code><div class="hljs-button {2}" data-title="複製" onclick="hljs.copyCode(event)"></div></pre>
<p> 爲變量賦值</p>
<pre class="has" name="code"><code class="hljs sql"><span class="hljs-keyword">SET</span> <span class="hljs-keyword">name</span> = <span class="hljs-string">'jay'</span>; <span class="hljs-comment">-- 爲name變量設置值</span></code><div class="hljs-button {2}" data-title="複製" onclick="hljs.copyCode(event)"></div></pre>
<pre class="has" name="code"><code class="hljs sql"><ol class="hljs-ln"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">DECLARE</span> var1,var2,var3 <span class="hljs-built_in">INT</span>;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">SET</span> var1 = <span class="hljs-number">10</span>,var2 = <span class="hljs-number">20</span>; <span class="hljs-comment">-- 其實爲了簡化記憶其語法，可以分開來寫</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="3"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment">-- SET var1 = 10;</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="4"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment">-- SET var2 = 20;</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="5"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">SET</span> var3 = var1 + var2;</div></div></li></ol></code><div class="hljs-button {2}" data-title="複製" onclick="hljs.copyCode(event)"></div></pre>
<p> 使用變量實例。如下表，在做了去除主鍵約束後，我又添加了一條id=1的數據。現在希望查詢出id爲1的記錄的數量。</p>
<p> <img alt="" class="has" height="94" src="https://img-blog.csdnimg.cn/20181103151418427.png" width="205"></p>
<pre class="has" name="code"><code class="hljs sql"><ol class="hljs-ln"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">DROP</span> <span class="hljs-keyword">PROCEDURE</span> <span class="hljs-keyword">IF</span> <span class="hljs-keyword">EXISTS</span> contStById;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> </div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="3"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">DELIMITER // <span class="hljs-comment">-- 定義存儲過程結束符號爲//</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="4"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">PROCEDURE</span> contStById(<span class="hljs-keyword">IN</span> <span class="hljs-keyword">sid</span> <span class="hljs-built_in">INT</span>(<span class="hljs-number">11</span>),<span class="hljs-keyword">OUT</span> <span class="hljs-keyword">result</span> <span class="hljs-built_in">INT</span>(<span class="hljs-number">11</span>)) <span class="hljs-comment">-- 定義輸入變量</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="5"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">BEGIN</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="6"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">DECLARE</span> sCount <span class="hljs-built_in">INT</span>;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="7"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">SELECT</span> <span class="hljs-keyword">COUNT</span>(*) <span class="hljs-keyword">INTO</span> sCount <span class="hljs-keyword">FROM</span> t_student <span class="hljs-keyword">WHERE</span> <span class="hljs-keyword">id</span> = <span class="hljs-keyword">sid</span>;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="8"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">SET</span> <span class="hljs-keyword">result</span> = sCount; <span class="hljs-comment">-- 用變量爲輸出結果設值</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="9"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">END</span> // <span class="hljs-comment">-- 結束符要加</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="10"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">DELIMITER ; <span class="hljs-comment">-- 重新定義存儲過程結束符爲分號</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="11"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> </div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="12"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">CALL</span> contStById(<span class="hljs-number">1</span>,@<span class="hljs-keyword">result</span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="13"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">SELECT</span> @<span class="hljs-keyword">result</span>;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="14"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> </div></div></li></ol></code><div class="hljs-button {2}" data-title="複製" onclick="hljs.copyCode(event)"></div></pre>
<p> <img alt="" class="has" height="75" src="https://img-blog.csdnimg.cn/20181103151548824.png" width="215"></p>
<p> 顯然，在存儲過程中的變量，可以直接與輸出變量進行相應的計算。本例直接把sCount這個變量的值賦值到輸出中。</p>
<h3><a name="t3" target="_blank"></a>10.1.4 定義條件與定義處理程序</h3>
<p> 定義條件CONDITION定義的是：在執行存儲過程中的SQL語句的時候，可能出現的問題。</p>
<p> 定義處理程序HANDLER：定義遇到了指定問題應該如何處理，避免存儲過程執行異常而停止。</p>
<p> 定義條件與定義處理語句程序的位置應該在BEGIN ... END 之間。</p>
<p> 定義條件的語法：DECLARE condtion_name CONDTION FOR 錯誤碼||錯誤值</p>
<p> 錯誤碼可以視爲一個錯誤的引用，比如404，它代表的就是找不到頁面的錯誤，它的錯誤值可以視爲NullPointerException。</p>
<pre class="has" name="code"><code class="hljs sql"><ol class="hljs-ln"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">DECLARE</span> command_not_allowed CONDITION <span class="hljs-keyword">FOR</span> <span class="hljs-keyword">SQLSTATE</span> <span class="hljs-string">'42000'</span>; <span class="hljs-comment">-- 錯誤值</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">DECLARE</span> command_not_allowed CONDITION <span class="hljs-keyword">FOR</span> <span class="hljs-number">1148</span>; <span class="hljs-comment">-- 錯誤碼</span></div></div></li></ol></code><div class="hljs-button {2}" data-title="複製" onclick="hljs.copyCode(event)"></div></pre>
<p> 定義處理程序語法：DECLARE HANDLER_TYPE HANDLER FOR condtion_name sp_statement；</p>
<p> MySQL定義了三種HANDLER_TYPE ，CONTIUE是指遇到錯誤忽略，繼續執行下面的SQL。EXIT表示遇到錯誤退出，默認的策略就是EXIT。</p>
<p> condtion_name可以是我們自己的定義的條件，也可以是MySQL內置的條件，比如SQLWARNING ，匹配01開頭的錯誤代碼。sp_statement指遇到錯誤的時候，需要執行的存儲過程或存儲函數。</p>
<p> <img alt="" class="has" height="143" src="https://img-blog.csdnimg.cn/20181103153425980.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmx1YW5kYWkxOTg1,size_16,color_FFFFFF,t_70" width="601"></p>
<pre class="has" name="code"><code class="hljs sql"><ol class="hljs-ln"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">DECLARE</span> CONTINUE <span class="hljs-keyword">HANDLER</span> <span class="hljs-keyword">FOR</span> SQLSATTE <span class="hljs-string">'42S02'</span> <span class="hljs-keyword">SET</span> @info = <span class="hljs-string">'NO_SUCH_TABLE'</span>; <span class="hljs-comment">-- 忽略錯誤值爲42S02的SQL異常</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> </div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="3"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">DECLARE</span> <span class="hljs-keyword">EXIT</span> <span class="hljs-keyword">HANDLER</span> <span class="hljs-keyword">FOR</span> SQLEXCEPTION <span class="hljs-keyword">SET</span> @info = <span class="hljs-string">'ERROR_OCCUR'</span>; <span class="hljs-comment">-- 捕獲SQL執行異常並輸出信息</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="4"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> </div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="5"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">DECLARE</span> no_such_table CONDITION <span class="hljs-keyword">FOR</span> <span class="hljs-number">1146</span>; <span class="hljs-comment">-- 爲錯誤碼爲1146的錯誤定義條件</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="6"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">DECLARE</span> CONTINUE <span class="hljs-keyword">HANDLER</span> <span class="hljs-keyword">FOR</span> no_such_table <span class="hljs-keyword">SET</span> @info = <span class="hljs-string">'no_such_table'</span>; <span class="hljs-comment">-- 爲指定的條件設置處理程序</span></div></div></li></ol></code><div class="hljs-button {2}" data-title="複製" onclick="hljs.copyCode(event)"></div></pre>
<pre class="has" name="code"><code class="hljs sql"><ol class="hljs-ln"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">DROP</span> <span class="hljs-keyword">TABLE</span> <span class="hljs-keyword">IF</span> <span class="hljs-keyword">EXISTS</span> t_student;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> </div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="3"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">TABLE</span> t_student</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="4"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">(</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="5"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">id</span> <span class="hljs-built_in">INT</span>(<span class="hljs-number">11</span>) PRIMARY <span class="hljs-keyword">KEY</span> AUTO_INCREMENT,</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="6"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">name</span> <span class="hljs-built_in">VARCHAR</span>(<span class="hljs-number">255</span>) <span class="hljs-keyword">NOT</span> <span class="hljs-literal">NULL</span>,</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="7"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> age <span class="hljs-built_in">INT</span>(<span class="hljs-number">11</span>) <span class="hljs-keyword">NOT</span> <span class="hljs-literal">NULL</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="8"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">);</div></div></li></ol></code><div class="hljs-button {2}" data-title="複製" onclick="hljs.copyCode(event)"></div></pre>
<p> <img alt="" class="has" height="63" src="https://img-blog.csdnimg.cn/20181103161859370.png" width="188"></p>
<p> 現通過存儲過程，爲這張表插入數據。因爲id屬性有主鍵約束，所以不能插入相同的id。</p>
<pre class="has" name="code"><code class="hljs sql"><ol class="hljs-ln"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">DROP</span> <span class="hljs-keyword">PROCEDURE</span> <span class="hljs-keyword">IF</span> <span class="hljs-keyword">EXISTS</span> insertStu;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> </div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="3"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">DELIMITER // <span class="hljs-comment">-- 定義存儲過程結束符號爲//</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="4"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">PROCEDURE</span> insertStu(<span class="hljs-keyword">OUT</span> <span class="hljs-keyword">result</span> <span class="hljs-built_in">INT</span>) <span class="hljs-comment">-- 指定輸出結果</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="5"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">BEGIN</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="6"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">DECLARE</span> flag <span class="hljs-built_in">INT</span>(<span class="hljs-number">11</span>) <span class="hljs-keyword">DEFAULT</span> <span class="hljs-number">0</span>; <span class="hljs-comment">-- 指定變量爲0</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="7"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">DECLARE</span> primary_key_limit CONDITION <span class="hljs-keyword">FOR</span> <span class="hljs-keyword">SQLSTATE</span> <span class="hljs-string">'23000'</span>; <span class="hljs-comment">-- 主鍵約束的錯誤值</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="8"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">DECLARE</span> CONTINUE <span class="hljs-keyword">HANDLER</span> <span class="hljs-keyword">FOR</span> primary_key_limit <span class="hljs-keyword">SET</span> @info = <span class="hljs-number">-1</span>; <span class="hljs-comment">-- 設計如果出現錯誤，@info將會被設置爲 -1 </span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="9"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">INSERT</span> <span class="hljs-keyword">INTO</span> t_student(<span class="hljs-keyword">id</span>,<span class="hljs-keyword">name</span>,age) <span class="hljs-keyword">VALUES</span>(<span class="hljs-number">1</span>,<span class="hljs-string">'dayu'</span>,<span class="hljs-number">22</span>); <span class="hljs-comment">-- 插入值，設置主鍵爲1</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="10"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">SET</span> flag = <span class="hljs-number">1</span>; <span class="hljs-comment">-- 普通變量設值爲1</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="11"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">SET</span> <span class="hljs-keyword">result</span> = flag; <span class="hljs-comment">-- 如果下面的SQL執行出現異常，那麼就退出，只有上面的SQL生效。將普通變量的值給輸出</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="12"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">INSERT</span> <span class="hljs-keyword">INTO</span> t_student(<span class="hljs-keyword">id</span>,<span class="hljs-keyword">name</span>,age) <span class="hljs-keyword">VALUES</span>(<span class="hljs-number">1</span>,<span class="hljs-string">'dayu'</span>,<span class="hljs-number">22</span>); <span class="hljs-comment">-- 插入值，設置主鍵爲1</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="13"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">SET</span> flag = <span class="hljs-number">2</span>; <span class="hljs-comment">-- 如果處理程序是EXIT，那麼就不會執行到這一步了</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="14"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">SET</span> <span class="hljs-keyword">result</span> = flag; <span class="hljs-comment">-- 將普通變量的值給輸出</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="15"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">END</span> // <span class="hljs-comment">-- 結束符要加</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="16"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">DELIMITER ; <span class="hljs-comment">-- 重新定義存儲過程結束符爲分號</span></div></div></li></ol></code><div class="hljs-button {2}" data-title="複製" onclick="hljs.copyCode(event)"></div></pre>
<p> CONTIUE是指遇到錯誤忽略，繼續執行下面的SQL。因爲是CONTINUE來處理程序，所以遇到錯誤將會繼續執行。</p>
<p> 另外，第二次插入記錄，因爲違反了主鍵約束，所以插入失敗，但是存儲過程仍然繼續執行完畢。</p>
<pre class="has" name="code"><code class="hljs sql"><ol class="hljs-ln"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">CALL</span> insertStu(@<span class="hljs-keyword">result</span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">SELECT</span> @<span class="hljs-keyword">result</span>,@info; <span class="hljs-comment">-- @info沒有申明就能調用到，可能是是全局變量吧</span></div></div></li></ol></code><div class="hljs-button {2}" data-title="複製" onclick="hljs.copyCode(event)"></div></pre>
<p> 運行結果： </p>
<p> <img alt="" class="has" height="78" src="https://img-blog.csdnimg.cn/20181103163720857.png" width="239"></p>
<p> 再次查看t_student表，只插入了一條記錄，但是所有的存儲過程都執行完畢了。 </p>
<p> <img alt="" class="has" height="87" src="https://img-blog.csdnimg.cn/20181103163752572.png" width="233"> </p>
<p> 現在，重新執行下面的SQL。先重新建表，再將處理程序的處理策略換爲EXIT：在執行存儲過程中遇到了錯誤，那麼就立即退出。</p>
<pre class="has" name="code"><code class="hljs sql"><ol class="hljs-ln"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">DROP</span> <span class="hljs-keyword">TABLE</span> <span class="hljs-keyword">IF</span> <span class="hljs-keyword">EXISTS</span> t_student;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> </div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="3"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">TABLE</span> t_student</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="4"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">(</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="5"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">id</span> <span class="hljs-built_in">INT</span>(<span class="hljs-number">11</span>) PRIMARY <span class="hljs-keyword">KEY</span> AUTO_INCREMENT,</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="6"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">name</span> <span class="hljs-built_in">VARCHAR</span>(<span class="hljs-number">255</span>) <span class="hljs-keyword">NOT</span> <span class="hljs-literal">NULL</span>,</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="7"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> age <span class="hljs-built_in">INT</span>(<span class="hljs-number">11</span>) <span class="hljs-keyword">NOT</span> <span class="hljs-literal">NULL</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="8"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="9"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> </div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="10"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">DROP</span> <span class="hljs-keyword">PROCEDURE</span> <span class="hljs-keyword">IF</span> <span class="hljs-keyword">EXISTS</span> insertStu;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="11"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> </div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="12"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">DELIMITER // <span class="hljs-comment">-- 定義存儲過程結束符號爲//</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="13"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">PROCEDURE</span> insertStu(<span class="hljs-keyword">OUT</span> <span class="hljs-keyword">result</span> <span class="hljs-built_in">INT</span>) <span class="hljs-comment">-- 指定輸出結果</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="14"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">BEGIN</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="15"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">DECLARE</span> flag <span class="hljs-built_in">INT</span>(<span class="hljs-number">11</span>) <span class="hljs-keyword">DEFAULT</span> <span class="hljs-number">0</span>; <span class="hljs-comment">-- 指定變量爲0</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="16"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">DECLARE</span> primary_key_limit CONDITION <span class="hljs-keyword">FOR</span> <span class="hljs-keyword">SQLSTATE</span> <span class="hljs-string">'23000'</span>; <span class="hljs-comment">-- 主鍵約束的錯誤值</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="17"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">DECLARE</span> <span class="hljs-keyword">EXIT</span> <span class="hljs-keyword">HANDLER</span> <span class="hljs-keyword">FOR</span> primary_key_limit <span class="hljs-keyword">SET</span> @info = <span class="hljs-number">-1</span>; <span class="hljs-comment">-- 使用EXIT策略，遇到SQL錯誤將會結束這次存儲過程</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="18"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-comment">-- 出現SQL錯誤則直接退出存儲過程的執行</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="19"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">INSERT</span> <span class="hljs-keyword">INTO</span> t_student(<span class="hljs-keyword">id</span>,<span class="hljs-keyword">name</span>,age) <span class="hljs-keyword">VALUES</span>(<span class="hljs-number">1</span>,<span class="hljs-string">'dayu'</span>,<span class="hljs-number">22</span>); <span class="hljs-comment">-- 插入值，設置主鍵爲1</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="20"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">SET</span> flag = <span class="hljs-number">1</span>; <span class="hljs-comment">-- 普通變量設值爲1</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="21"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">SET</span> <span class="hljs-keyword">result</span> = flag; <span class="hljs-comment">-- 如果下面的SQL執行出現異常，那麼就退出，只有上面的SQL生效。將普通變量的值給輸出</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="22"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">INSERT</span> <span class="hljs-keyword">INTO</span> t_student(<span class="hljs-keyword">id</span>,<span class="hljs-keyword">name</span>,age) <span class="hljs-keyword">VALUES</span>(<span class="hljs-number">1</span>,<span class="hljs-string">'dayu'</span>,<span class="hljs-number">22</span>); <span class="hljs-comment">-- 插入值，設置主鍵爲1</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="23"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">SET</span> flag = <span class="hljs-number">2</span>; <span class="hljs-comment">-- 如果處理程序是EXIT，那麼就不會執行到這一步了</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="24"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">SET</span> <span class="hljs-keyword">result</span> = flag; <span class="hljs-comment">-- 將普通變量的值給輸出</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="25"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">END</span> // <span class="hljs-comment">-- 結束符要加</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="26"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">DELIMITER ; <span class="hljs-comment">-- 重新定義存儲過程結束符爲分號</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="27"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> </div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="28"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">CALL</span> insertStu(@<span class="hljs-keyword">result</span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="29"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">SELECT</span> @<span class="hljs-keyword">result</span>,@info; <span class="hljs-comment">-- @info沒有申明就能調用到，可能是是全局變量吧</span></div></div></li></ol></code><div class="hljs-button {2}" data-title="複製" onclick="hljs.copyCode(event)"></div></pre>
<p> <img alt="" class="has" height="84" src="https://img-blog.csdnimg.cn/20181103164240503.png" width="223"> </p>
<p> @result的結果爲1，說明執行第二條SQL的時候，出現了異常。同樣，@info的值爲-1，也提示處理條件中定義的存儲過程被觸發。最後，數據庫表中的數據也是</p>
<p><img alt="" class="has" height="57" src="https://img-blog.csdnimg.cn/20181103164919201.png" width="221"></p>
<p> 如果都是正確的SQL，會是什麼情況呢？</p>
<pre class="has" name="code"><code class="hljs sql"><ol class="hljs-ln"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">DROP</span> <span class="hljs-keyword">TABLE</span> <span class="hljs-keyword">IF</span> <span class="hljs-keyword">EXISTS</span> t_student;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> </div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="3"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">TABLE</span> t_student</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="4"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">(</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="5"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">id</span> <span class="hljs-built_in">INT</span>(<span class="hljs-number">11</span>) PRIMARY <span class="hljs-keyword">KEY</span> AUTO_INCREMENT,</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="6"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">name</span> <span class="hljs-built_in">VARCHAR</span>(<span class="hljs-number">255</span>) <span class="hljs-keyword">NOT</span> <span class="hljs-literal">NULL</span>,</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="7"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> age <span class="hljs-built_in">INT</span>(<span class="hljs-number">11</span>) <span class="hljs-keyword">NOT</span> <span class="hljs-literal">NULL</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="8"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="9"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> </div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="10"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">DROP</span> <span class="hljs-keyword">PROCEDURE</span> <span class="hljs-keyword">IF</span> <span class="hljs-keyword">EXISTS</span> insertStu;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="11"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> </div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="12"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">DELIMITER // <span class="hljs-comment">-- 定義存儲過程結束符號爲//</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="13"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">PROCEDURE</span> insertStu(<span class="hljs-keyword">OUT</span> <span class="hljs-keyword">result</span> <span class="hljs-built_in">INT</span>) <span class="hljs-comment">-- 指定輸出結果</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="14"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">BEGIN</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="15"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">DECLARE</span> flag <span class="hljs-built_in">INT</span>(<span class="hljs-number">11</span>) <span class="hljs-keyword">DEFAULT</span> <span class="hljs-number">0</span>; <span class="hljs-comment">-- 指定變量爲0</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="16"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">DECLARE</span> primary_key_limit CONDITION <span class="hljs-keyword">FOR</span> <span class="hljs-keyword">SQLSTATE</span> <span class="hljs-string">'23000'</span>; <span class="hljs-comment">-- 主鍵約束的錯誤值</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="17"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">DECLARE</span> <span class="hljs-keyword">EXIT</span> <span class="hljs-keyword">HANDLER</span> <span class="hljs-keyword">FOR</span> primary_key_limit <span class="hljs-keyword">SET</span> @info = <span class="hljs-number">-1</span>; <span class="hljs-comment">-- 設計如果出現錯誤，@info將會被設置爲 -1 </span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="18"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">INSERT</span> <span class="hljs-keyword">INTO</span> t_student(<span class="hljs-keyword">id</span>,<span class="hljs-keyword">name</span>,age) <span class="hljs-keyword">VALUES</span>(<span class="hljs-literal">NULL</span>,<span class="hljs-string">'dayu'</span>,<span class="hljs-number">22</span>); <span class="hljs-comment">-- </span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="19"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">SET</span> flag = <span class="hljs-number">1</span>; <span class="hljs-comment">-- 普通變量設值爲1</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="20"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">SET</span> <span class="hljs-keyword">result</span> = flag; <span class="hljs-comment">-- 如果下面的SQL執行出現異常，那麼就退出，只有上面的SQL生效。將普通變量的值給輸出</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="21"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">INSERT</span> <span class="hljs-keyword">INTO</span> t_student(<span class="hljs-keyword">id</span>,<span class="hljs-keyword">name</span>,age) <span class="hljs-keyword">VALUES</span>(<span class="hljs-literal">NULL</span>,<span class="hljs-string">'dayu'</span>,<span class="hljs-number">22</span>); <span class="hljs-comment">-- </span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="22"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">SET</span> flag = <span class="hljs-number">2</span>; <span class="hljs-comment">-- 如果處理程序是EXIT，那麼就不會執行到這一步了</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="23"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword">SET</span> <span class="hljs-keyword">result</span> = flag; <span class="hljs-comment">-- 將普通變量的值給輸出</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="24"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">END</span> // <span class="hljs-comment">-- 結束符要加</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="25"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">DELIMITER ; <span class="hljs-comment">-- 重新定義存儲過程結束符爲分號</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="26"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> </div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="27"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">CALL</span> insertStu(@<span class="hljs-keyword">result</span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="28"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">SELECT</span> @<span class="hljs-keyword">result</span>,@info; <span class="hljs-comment">-- @info沒有申明就能調用到，可能是是全局變量吧</span></div></div></li></ol></code><div class="hljs-button {2}" data-title="複製" onclick="hljs.copyCode(event)"></div></pre>
<p> <img alt="" class="has" height="72" src="https://img-blog.csdnimg.cn/20181103165434188.png" width="211"></p>
<p> <img alt="" class="has" height="71" src="https://img-blog.csdnimg.cn/2018110316544823.png" width="204"></p>
<p> 很奇怪，書上說如果遇到異常，將會執行定義條件後面的存儲過程，但是從實際情況來看，當前的存儲過程都是正確的，@info變量的值卻也是-1，我自己也不是太能理解。@result的值爲2的結果說明了存儲過程執行到結尾。從表中的結果來看，也是正確的插入了兩條數據。</p>
<p> 在回頭琢磨一下書的話：sp_statement參數爲程序語句段，表示在遇到定義錯誤時，需要執行的存儲過程或者函數。可能這裏欠妥吧。</p>
<p> 總之，下面的核心知識點沒有疑問：在聲明條件後並遇到相關的錯誤條件後，那就看應該怎麼處理。如果是EXIT，那麼存儲過程只生效到錯誤處的上一條SQL。如果是CONTINUE，那麼將會忽略掉執行錯誤的SQL，繼續執行下面的其它存儲過程。</p>
<h3><a name="t4" target="_blank"></a>閱讀更多</h3>
<p> <a href="https://blog.csdn.net/yanluandai1985/article/details/83656374" rel="nofollow" data-token="945ce2514f0b0d9ced635cfac5dab479" target="_blank">從頭開始學MySQL-------存儲過程與存儲函數（1）</a></p>
<p> <a href="https://blog.csdn.net/yanluandai1985/article/details/83689524" rel="nofollow" data-token="3e8d0bd2c27233fe4dc9cf511a932cfd" target="_blank"> 從頭開始學MySQL-------存儲過程與存儲函數（2）</a></p>
<p> <a href="https://blog.csdn.net/yanluandai1985/article/details/83653712" rel="nofollow" data-token="6150df0a2bd71af32ad13914b2c885c4" target="_blank">從頭開始學MySQL-------存儲過程與存儲函數（3）</a></p>
<p> <a href="https://blog.csdn.net/yanluandai1985/article/details/83715441" rel="nofollow" data-token="67782129d837d1304fc58c3923f7ea4f" target="_blank">從頭開始學MySQL-------存儲過程與存儲函數（4）</a></p>
<p> 目錄貼：<a href="https://blog.csdn.net/yanluandai1985/article/details/89632265" rel="nofollow" data-token="8c005f49e9d9a452973fa69cb0ad370c" target="_blank">從頭開始學MySQL-------目錄帖</a></p>
<p> </p>
<p> </p>
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<p> </p>
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