当 CHAR_LENGTH() 或 CHARACTER_LENGTH() 字符串函数与 WHERE 子句一起使用时，其返回的输出将取决于 WHERE 子句中给出的条件。例如，假设我们有一个名为“Student”的表，并且我们只想获取那些字符数小于 6 的姓名，那么我们可以编写以下查询 -
mysql> Select * from Student; +------+---------+---------+-----------+ | Id | Name | Address | Subject | +------+---------+---------+-----------+ | 1 | Gaurav | Delhi | Computers | | 2 | Aarav | Mumbai | History | | 15 | Harshit | Delhi | Commerce | | 20 | Gaurav | Jaipur | Computers | +------+---------+---------+-----------+ 4 rows in set (0.10 sec) mysql> Select Name, CHAR_LENGTH(Name) from student WHERE CHAR_LENGTH(Name)<6; +-------+-------------------+ | Name | CHAR_LENGTH(Name) | +-------+-------------------+ | Aarav | 5 | +-------+-------------------+ 1 row in set (0.00 sec)
