见字如面,如标题拆分:分组 GROUP BY field_name统计 COUNT(field_name)去重 DISTINCT field_name条件过滤 CASE WHEN age > 18 THEN age END示例:前序:(表结构)CREATE TABLE `data
操作:首先创建个表,把要删除那个表重复记录的最大ID读出来然后执行删除最后把创建的那个表删除了$db->query("create table tmp as select max(id) as col1 from `表名` group by `需要删除的重复数据的字段名`");$
create procedure p_test begin if s < 5000。then select name,salary,gender from emp where salary <5000;