mysql中读取一个字符串长度的示例：

mysql>select*fromtest;
+----+------------+-------+-----------+
|id|name|score|subject|
+----+------------+-------+-----------+
|1|xiaoming|89|shuxue|
|2|xiaohong|89|shuxue|
|3|xiaohong|80|english|
|4|xiaohong|80|physics|
|5|xiaohong|80|astronaut|
|6|xiaoming|80|physics|
|7|xiaoming|80|astronaut|
|8|xiaoming|80|english|
|9|xiaobai|80|astronaut|
|10|1.2xiaobai|80|english|
|11|2.2xiaobai|80|physics|
|12|3xiaobai|80|shuxue|
|13|123xiaohei|80|astronaut|
|14|xiaohei|80|shuxue|
|15|xiaohei|80|physics|
|16|.12xiaohei|80|english|
+----+------------+-------+-----------+
16rowsinset(0.00sec)
mysql>selectlength(name)fromtestwhereid=3;（查询id为3的name字符串长度）
+--------------+
|length(name)|
+--------------+
|8|
+--------------+
1rowinset(0.00sec)