字符串函数

mysql> select ascii("w");
+------------+
| ascii("w") |
+------------+
|        119 |
+------------+
1 row in set (0.00 sec)

mysql> select char(119);
+-----------+
| char(119) |
+-----------+
| w         |
+-----------+
1 row in set (0.00 sec)

mysql> select repeat("w",10);
+----------------+
| repeat("w",10) |
+----------------+
| wwwwwwwwww     |
+----------------+
1 row in set (0.00 sec)


mysql> select length("是");
+---------------+
| length("是")  |
+---------------+
|             3 |
+---------------+
1 row in set (0.17 sec)

mysql> select char_length("是"); 
+--------------------+
| char_length("是")  |
+--------------------+
|                  1 |
+--------------------+
1 row in set (0.00 sec)

mysql> select concat("a","b");
+-----------------+
| concat("a","b") |
+-----------------+
| ab              |
+-----------------+
1 row in set (0.00 sec)


mysql> select lower("A");
+------------+
| lower("A") |
+------------+
| a          |
+------------+
1 row in set (0.00 sec)

mysql> select upper("a");
+------------+
| upper("a") |
+------------+
| A          |
+------------+
1 row in set (0.00 sec)

mysql> select instr("this is test","test");
+------------------------------+
| instr("this is test","test") |
+------------------------------+
|                            9 |
+------------------------------+
1 row in set (0.00 sec)

mysql> select instr("this is test","t");
+---------------------------+
| instr("this is test","t") |
+---------------------------+
|                         1 |
+---------------------------+
1 row in set (0.00 sec)


mysql> select left("abcdef",2);
+------------------+
| left("abcdef",2) |
+------------------+
| ab               |
+------------------+
1 row in set (0.00 sec)

mysql> select right("abcdef",2);    
+-------------------+
| right("abcdef",2) |
+-------------------+
| ef                |
+-------------------+
1 row in set (0.00 sec)




mysql> select replace("abcdef","abc","ABC"); 
+-------------------------------+
| replace("abcdef","abc","ABC") |
+-------------------------------+
| ABCdef                        |
+-------------------------------+
1 row in set (0.00 sec)

mysql> select trim(" abcd ");
+----------------+
| trim(" abcd ") |
+----------------+
| abcd           |
+----------------+
1 row in set (0.00 sec)