【筆記四】：LIKE，UNION，ORDER BY，AND，OR，IN，BETWEEN，IS NULL，NOT

1，LIKE

以下是 SQL SELECT 語句使用 LIKE 子句從數據表中讀取數據的通用語法：

SELECT field1, field2,...fieldN 
FROM table_name
WHERE field1 LIKE condition1 [AND [OR]] filed2 = 'somevalue'

%：表示任意 0 個或多個字符。可匹配任意類型和長度的字符，有些情況下若是中文，請使用兩個百分號（%%）表示。
_：表示任意單個字符。匹配單個任意字符，它常用來限制表達式的字符長度語句。
[]：表示括號內所列字符中的一個（類似正則表達式）。指定一個字符、字符串或範圍，要求所匹配對象爲它們中的任一個。
[^] ：表示不在括號所列之內的單個字符。其取值和 [] 相同，但它要求所匹配對象爲指定字符以外的任一個字符。
查詢內容包含通配符時,由於通配符的緣故，導致我們查詢特殊字符 “%”、“_”、“[” 的語句無法正常實現，而把特殊字符用 “[ ]” 括起便可正常查詢

MariaDB [mydb]> select * from students;
+-------+-----------+------+------+----------+------------+
| id    | name      | sex  | age  | interest | birthday   |
+-------+-----------+------+------+----------+------------+
| 20001 | 小明      | 男   |   16 | football | 2004-03-05 |
| 20002 | 小紅      | 女   |   14 | music    | 2006-06-18 |
| 20003 | 小張      | 男   |   15 | painting | 2005-08-14 |
| 20004 | 露絲      | 女   |   13 | painting | 2007-07-19 |
| 20005 | 麗麗      | 女   |   15 | painting | 2005-12-01 |
| 20005 | 李明      | 男   |   16 | music    | 2004-08-14 |
| 20006 | 張大明    | 男   |   18 | football | 2002-03-05 |
+-------+-----------+------+------+----------+------------+
7 rows in set (0.001 sec)

選擇birthday 是03月份的學生

MariaDB [mydb]> select * from students where birthday like '%03%';
+-------+-----------+------+------+----------+------------+
| id    | name      | sex  | age  | interest | birthday   |
+-------+-----------+------+------+----------+------------+
| 20001 | 小明      | 男   |   16 | football | 2004-03-05 |
| 20006 | 張大明    | 男   |   18 | football | 2002-03-05 |
+-------+-----------+------+------+----------+------------+
2 rows in set (0.000 sec)

選擇name是2個字且最後一個字是‘明’的學生

MariaDB [mydb]> select * from students where name like '_明';
+-------+--------+------+------+----------+------------+
| id    | name   | sex  | age  | interest | birthday   |
+-------+--------+------+------+----------+------------+
| 20001 | 小明   | 男   |   16 | football | 2004-03-05 |
| 20005 | 李明   | 男   |   16 | music    | 2004-08-14 |
+-------+--------+------+------+----------+------------+
2 rows in set (0.002 sec)

選擇除了name是2個字且最後一個字是‘明’以外的學生

MariaDB [mydb]> select * from students where birthday not like '%03%';
+-------+--------+------+------+----------+------------+
| id    | name   | sex  | age  | interest | birthday   |
+-------+--------+------+------+----------+------------+
| 20002 | 小紅   | 女   |   14 | music    | 2006-06-18 |
| 20003 | 小張   | 男   |   15 | painting | 2005-08-14 |
| 20004 | 露絲   | 女   |   13 | painting | 2007-07-19 |
| 20005 | 麗麗   | 女   |   15 | painting | 2005-12-01 |
| 20005 | 李明   | 男   |   16 | music    | 2004-08-14 |
+-------+--------+------+------+----------+------------+
5 rows in set (0.002 sec)

2，ORDER BY

按age升序、降序排列

SELECT field, field2,... [or column] FROM table_name, table_name2,...
ORDER BY field, field2,... ASC[or DESC]

默認是按升序排列 [ASC]

MariaDB [mydb]> select * from students order by age;
+-------+-----------+------+------+------------+------------+
| id    | name      | sex  | age  | interest   | birthday   |
+-------+-----------+------+------+------------+------------+
| 20004 | 露絲      | 女   |   13 | painting   | 2007-07-19 |
| 20002 | 小紅      | 女   |   14 | music      | 2006-06-18 |
| 20003 | 小張      | 男   |   15 | basketball | 2005-08-14 |
| 20005 | 麗麗      | 女   |   15 | painting   | 2005-12-01 |
| 20001 | 小明      | 男   |   16 | football   | 2004-03-05 |
| 20005 | 李明      | 男   |   16 | music      | 2004-08-14 |
| 20006 | 張大明    | 男   |   18 | football   | 2002-03-05 |
+-------+-----------+------+------+------------+------------+
7 rows in set (0.000 sec)

指定age按降序排列。

MariaDB [mydb]> select * from students order by age desc;
+-------+-----------+------+------+------------+------------+
| id    | name      | sex  | age  | interest   | birthday   |
+-------+-----------+------+------+------------+------------+
| 20006 | 張大明    | 男   |   18 | football   | 2002-03-05 |
| 20001 | 小明      | 男   |   16 | football   | 2004-03-05 |
| 20005 | 李明      | 男   |   16 | music      | 2004-08-14 |
| 20003 | 小張      | 男   |   15 | basketball | 2005-08-14 |
| 20005 | 麗麗      | 女   |   15 | painting   | 2005-12-01 |
| 20002 | 小紅      | 女   |   14 | music      | 2006-06-18 |
| 20004 | 露絲      | 女   |   13 | painting   | 2007-07-19 |
+-------+-----------+------+------+------------+------------+
7 rows in set (0.000 sec)

先指定age按升序排列如果age相同brithday再按降序排列。

MariaDB [mydb]> select * from students order by age, birthday desc;
+-------+-----------+------+------+------------+------------+
| id    | name      | sex  | age  | interest   | birthday   |
+-------+-----------+------+------+------------+------------+
| 20004 | 露絲      | 女   |   13 | painting   | 2007-07-19 |
| 20002 | 小紅      | 女   |   14 | music      | 2006-06-18 |
| 20005 | 麗麗      | 女   |   15 | painting   | 2005-12-01 |
| 20003 | 小張      | 男   |   15 | basketball | 2005-08-14 |
| 20006 | 李明      | 男   |   16 | music      | 2004-08-14 |
| 20001 | 小明      | 男   |   16 | football   | 2004-03-05 |
| 20007 | 張大明    | 男   |   18 | football   | 2002-03-05 |
+-------+-----------+------+------+------------+------------+
7 rows in set (0.001 sec)

3，UNION

操作符用於合併兩個或多個 SELECT 語句的結果集。請注意，UNION 內部的 SELECT 語句必須擁有相同數量的列。列也必須擁有相似的數據類型。同時，每條 SELECT 語句中的列的順序必須相同。

SQL UNION 語法

SELECT column_name(s) FROM table_name1
UNION
SELECT column_name(s) FROM table_name2

註釋：默認地，UNION 操作符選取不同的值。如果允許重複的值，請使用 UNION ALL。

SQL UNION ALL 語法
SELECT column_name(s) FROM table_name1
UNION ALL
SELECT column_name(s) FROM table_name2

另外，UNION 結果集中的列名總是等於 UNION 中第一個 SELECT 語句中的列名。

以下2張表

MariaDB [mydb]> select * from students;
+-------+-----------+------+------+------------+------------+
| id    | name      | sex  | age  | interest   | birthday   |
+-------+-----------+------+------+------------+------------+
| 20001 | 小明      | 男   |   16 | football   | 2004-03-05 |
| 20002 | 小紅      | 女   |   14 | music      | 2006-06-18 |
| 20003 | 小張      | 男   |   15 | basketball | 2005-08-14 |
| 20004 | 露絲      | 女   |   13 | painting   | 2007-07-19 |
| 20005 | 麗麗      | 女   |   15 | painting   | 2005-12-01 |
| 20006 | 李明      | 男   |   16 | music      | 2004-08-14 |
| 20007 | 張大明    | 男   |   18 | football   | 2002-03-05 |
+-------+-----------+------+------+------------+------------+
7 rows in set (0.002 sec)

MariaDB [mydb]> select * from score;
+-------+-----------+------+----------+--------+
| id    | name      | math | language | sports |
+-------+-----------+------+----------+--------+
| 20001 | 小明      |   81 |       86 |     93 |
| 20002 | 小紅      |   86 |       86 |     89 |
| 20003 | 小張      |   77 |       83 |     93 |
| 20004 | 露絲      |   88 |       78 |     65 |
| 20005 | 麗麗      |   92 |       94 |     64 |
| 20006 | 李明      |   75 |       78 |     88 |
| 20007 | 張大明    |   54 |       65 |     95 |
+-------+-----------+------+----------+--------+
7 rows in set (0.000 sec)

MariaDB [mydb]> select id,name from students union select id,name from score;
+-------+-----------+
| id    | name      |
+-------+-----------+
| 20001 | 小明      |
| 20002 | 小紅      |
| 20003 | 小張      |
| 20004 | 露絲      |
| 20005 | 麗麗      |
| 20006 | 李明      |
| 20007 | 張大明    |
+-------+-----------+
7 rows in set (0.002 sec)

MariaDB [mydb]> select id,name from students union all select id,name from score;
+-------+-----------+
| id    | name      |
+-------+-----------+
| 20001 | 小明      |
| 20002 | 小紅      |
| 20003 | 小張      |
| 20004 | 露絲      |
| 20005 | 麗麗      |
| 20006 | 李明      |
| 20007 | 張大明    |
| 20001 | 小明      |
| 20002 | 小紅      |
| 20003 | 小張      |
| 20004 | 露絲      |
| 20005 | 麗麗      |
| 20006 | 李明      |
| 20007 | 張大明    |
+-------+-----------+
14 rows in set (0.002 sec)

4，AND

MariaDB [mydb]> select * from students where age=16 and interest='music';
+-------+--------+------+------+----------+------------+
| id    | name   | sex  | age  | interest | birthday   |
+-------+--------+------+------+----------+------------+
| 20006 | 李明   | 男   |   16 | music    | 2004-08-14 |
+-------+--------+------+------+----------+------------+
1 row in set (0.001 sec)

5，OR

MariaDB [mydb]> select * from students where age=16 or birthday='2007-07-19';
+-------+--------+------+------+----------+------------+
| id    | name   | sex  | age  | interest | birthday   |
+-------+--------+------+------+----------+------------+
| 20001 | 小明   | 男   |   16 | football | 2004-03-05 |
| 20004 | 露絲   | 女   |   13 | painting | 2007-07-19 |
| 20006 | 李明   | 男   |   16 | music    | 2004-08-14 |
+-------+--------+------+------+----------+------------+
3 rows in set (0.000 sec)

MariaDB [mydb]> select * from students where (age=16 and birthday='2004-08-14') or birthday='2007-07-19';
+-------+--------+------+------+----------+------------+
| id    | name   | sex  | age  | interest | birthday   |
+-------+--------+------+------+----------+------------+
| 20004 | 露絲   | 女   |   13 | painting | 2007-07-19 |
| 20006 | 李明   | 男   |   16 | music    | 2004-08-14 |
+-------+--------+------+------+----------+------------+
2 rows in set (0.002 sec)

6，IN

MariaDB [mydb]> select * from students where age in (13,14);
+-------+--------+------+------+----------+------------+
| id    | name   | sex  | age  | interest | birthday   |
+-------+--------+------+------+----------+------------+
| 20002 | 小紅   | 女   |   14 | music    | 2006-06-18 |
| 20004 | 露絲   | 女   |   13 | painting | 2007-07-19 |
+-------+--------+------+------+----------+------------+
2 rows in set (0.001 sec)

7，BETWEEN AND

MariaDB [mydb]> select * from students where age between 15 and 18;
+-------+-----------+------+------+------------+------------+
| id    | name      | sex  | age  | interest   | birthday   |
+-------+-----------+------+------+------------+------------+
| 20001 | 小明      | 男   |   16 | football   | 2004-03-05 |
| 20003 | 小張      | 男   |   15 | basketball | 2005-08-14 |
| 20005 | 麗麗      | 女   |   15 | painting   | 2005-12-01 |
| 20006 | 李明      | 男   |   16 | music      | 2004-08-14 |
| 20007 | 張大明    | 男   |   18 | football   | 2002-03-05 |
+-------+-----------+------+------+------------+------------+
5 rows in set (0.000 sec)

8，IS NULL

首先確保我的表格中的某些數據是null纔可以使用
update colin set name='Chen' where age=null;
是修改不了數據的因爲age=null 最後的結果是false 條件是不成立的
update colin set name='Chen' where 1=1; 條件成立，但是這種條件沒有任何意義
update colin set name='Chen' where age is null; 正確

9，NOT

MariaDB [mydb]> select * from students where not age=15;
+-------+-----------+------+------+----------+------------+
| id    | name      | sex  | age  | interest | birthday   |
+-------+-----------+------+------+----------+------------+
| 20001 | 小明      | 男   |   16 | football | 2004-03-05 |
| 20002 | 小紅      | 女   |   14 | music    | 2006-06-18 |
| 20004 | 露絲      | 女   |   13 | painting | 2007-07-19 |
| 20006 | 李明      | 男   |   16 | music    | 2004-08-14 |
| 20007 | 張大明    | 男   |   18 | football | 2002-03-05 |
+-------+-----------+------+------+----------+------------+
5 rows in set (0.000 sec)
MariaDB [mydb]> select * from students where age not between 15 and 18;
+-------+--------+------+------+----------+------------+
| id    | name   | sex  | age  | interest | birthday   |
+-------+--------+------+------+----------+------------+
| 20002 | 小紅   | 女   |   14 | music    | 2006-06-18 |
| 20004 | 露絲   | 女   |   13 | painting | 2007-07-19 |
+-------+--------+------+------+----------+------------+
2 rows in set (0.001 sec)

【筆記四】：LIKE，UNION，ORDER BY，AND，OR，IN，BETWEEN，IS NULL，NOT

1，LIKE

2，ORDER BY

3，UNION

4，AND

5，OR

6，IN

7，BETWEEN AND

8，IS NULL

9，NOT

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