[TOC] # 查询时间，友好提示 * timestamp 日期类型 ~~~ $sql = "select date_format(create_time, '%Y-%m-%d') as day from table_name"; ~~~ * int 时间戳类型 ~~~ $sql = "select from_unixtime(create_time, '%Y-%m-%d') as day from table_name"; ~~~ # 一个sql 返回多个总数 ~~~ $sql = "select count(*) all, " ; $sql .= " count(case when status = 1 then status end) status_1_num, "; $sql .= " count(case when status = 2 then status end) status_2_num "; $sql .= " from table_name"; ~~~ # Update Join / Delete Join ~~~ $sql = "update table_name_1 "; $sql .= " inner join table_name_2 on table_name_1.id = table_name_2.uid "; $sql .= " inner join table_name_3 on table_name_3.id = table_name_1.tid "; $sql .= " set *** = *** "; $sql .= " where *** "; //delete join 同上。 ~~~ # 替换某字段的内容的语句 ~~~ $sql = "update table_name set content = REPLACE(content, 'aaa', 'bbb') "; $sql .= " where (content like '%aaa%')"; ~~~ # 获取表中某字段包含某字符串的数据 ~~~ $sql = "SELECT * FROM `表名` WHERE LOCATE('关键字', 字段名) "; ~~~ # 获取字段中的前4位 ~~~ $sql = "SELECT SUBSTRING(字段名,1,4) FROM 表名 "; ~~~ # 查找表中多余的重复记录 * 单个字段 ~~~ $sql = "select * from 表名 where 字段名 in "; $sql .= "(select 字段名 from 表名 group by 字段名 having count(字段名) > 1 )"; ~~~ * 多个字段 ~~~ $sql = "select * from 表名 别名 where (别名.字段1,别名.字段2) in "; $sql .= "(select 字段1,字段2 from 表名 group by 字段1,字段2 having count(*) > 1 )"; ~~~ # 删除表中多余的重复记录(留id最小) * 单个字段 ~~~ $sql = "delete from 表名 where 字段名 in "; $sql .= "(select 字段名 from 表名 group by 字段名 having count(字段名) > 1) "; $sql .= "and 主键ID not in "; $sql .= "(select min(主键ID) from 表名 group by 字段名 having count(字段名 )>1) "; ~~~ * 多个字段 ~~~ $sql = "delete from 表名 别名 where (别名.字段1,别名.字段2) in "; $sql .= "(select 字段1,字段2 from 表名 group by 字段1,字段2 having count(*) > 1) "; $sql .= "and 主键ID not in "; $sql .= "(select min(主键ID) from 表名 group by 字段1,字段2 having count(*)>1) "; ~~~