https://blog.csdn.net/wpfphp/article/details/52584232
https://blog.csdn.net/shellching/article/details/8098120
instr語法
語法如下：
instr( string1, string2, start_position,nth_appearance ) [1] [2]
|
string1 |
源字符串，要在此字符串中查找。 |
|
string2 |
要在string1中查找的字符串 。 |
|
start_position |
代表string1 的哪個位置開始查找。此參數可選，如果省略默認爲1. 字符串索引從1開始。如果此參數爲正，從左到右開始檢索，如果此參數爲負，從右到左檢索，返回要查找的字符串在源字符串中的開始索引。 |
|
nth_appearance |
代表要查找第幾次出現的string2. 此參數可選，如果省略，默認爲 1.如果爲負數系統會報錯。 |
注意一點，locate語句後面設置<0, >0 , =0的區別：
mysql> select*from `runoob_tbl`;
+-----------+--------------+------------------+-----------------+
| runoob_id | runoob_title | runoob_author | submission_date |
+-----------+--------------+------------------+-----------------+
| 1 | 學習 PHP | 爆炸菜鳥教程爆炸 | 2018-08-15 |
| 2 | 學習 MySQL | 菜鳥教程 | 2018-08-15 |
| 3 | 學習 C++ | RUNOOB.COM | 2016-05-06 |
| 4 | JAVA 教程 | RUNOOB.COM | 2016-03-06 |
| 5 | 連接 | 隨便寫 | 2018-08-18 |
+-----------+--------------+------------------+-----------------+
mysql> select*from `runoob_tbl` where locate('教程',`runoob_author`)>0;
+-----------+--------------+------------------+-----------------+
| runoob_id | runoob_title | runoob_author | submission_date |
+-----------+--------------+------------------+-----------------+
| 1 | 學習 PHP | 爆炸菜鳥教程爆炸 | 2018-08-15 |
| 2 | 學習 MySQL | 菜鳥教程 | 2018-08-15 |
+-----------+--------------+------------------+-----------------+
2 rows in set
mysql> select*from `runoob_tbl` where locate('教程',`runoob_author`)<0;
Empty set
mysql> select*from `runoob_tbl` where locate('教程',`runoob_author`)=0;
+-----------+--------------+---------------+-----------------+
| runoob_id | runoob_title | runoob_author | submission_date |
+-----------+--------------+---------------+-----------------+
| 3 | 學習 C++ | RUNOOB.COM | 2016-05-06 |
| 4 | JAVA 教程 | RUNOOB.COM | 2016-03-06 |
| 5 | 連接 | 隨便寫 | 2018-08-18 |
+-----------+--------------+---------------+-----------------+
3 rows in set
- 語句結構：
- LOCATE(substr,str) , LOCATE(substr,str,pos)
- FIND_IN_SET(substr,strlist)
like是廣泛的模糊匹配，字符串中沒有分隔符，find_in_set是精確匹配，字段值以英文”,”分隔， 注意 find_in_set 是全表掃描的
例：
mysql> select*from `runoob_tbl`;
+-----------+--------------+------------------+-----------------+
| runoob_id | runoob_title | runoob_author | submission_date |
+-----------+--------------+------------------+-----------------+
| 1 | 學習 PHP | 爆炸菜鳥教程爆炸 | 2018-08-15 |
| 2 | 學習 MySQL | 菜鳥教程 | 2018-08-15 |
| 3 | 學習 C++ | RUNOOB.COM | 2016-05-06 |
| 4 | JAVA 教程 | RUNOOB.COM | 2016-03-06 |
| 5 | 連接 | 隨便寫 | 2018-08-18 |
+-----------+--------------+------------------+-----------------+
5 rows in set
mysql> select*from `runoob_tbl` where find_in_set('菜鳥教程',`runoob_author`);
+-----------+--------------+---------------+-----------------+
| runoob_id | runoob_title | runoob_author | submission_date |
+-----------+--------------+---------------+-----------------+
| 2 | 學習 MySQL | 菜鳥教程 | 2018-08-15 |
+-----------+--------------+---------------+-----------------+
1 row in set
#find_in_set後跟完整的字符串'菜鳥教程'可選出結果。
否則，結果爲空：
mysql> select*from `runoob_tbl` where find_in_set('教程',`runoob_author`)>0;
Empty set
若設置find_in_set=0,則選出的結果爲不包含'菜鳥教程'的內容：
mysql> select*from `runoob_tbl` where find_in_set('菜鳥教程',`runoob_author`)=0;
+-----------+--------------+------------------+-----------------+
| runoob_id | runoob_title | runoob_author | submission_date |
+-----------+--------------+------------------+-----------------+
| 1 | 學習 PHP | 爆炸菜鳥教程爆炸 | 2018-08-15 |
| 3 | 學習 C++ | RUNOOB.COM | 2016-05-06 |
| 4 | JAVA 教程 | RUNOOB.COM | 2016-03-06 |
| 5 | 連接 | 隨便寫 | 2018-08-18 |
+-----------+--------------+------------------+-----------------+
4 rows in set
- INSTR(str,substr)
- POSITION(substr IN str) 其中substr爲需要查找的字符串，str及strlist爲查找範圍。
關於大小寫敏感問題：https://blog.csdn.net/qq_27682041/article/details/73647706