** 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) ";
查询表的创建时间
USE information_schema;
SELECT CREATE_TIME FROM TABLES WHERE TABLE_SCHEMA='数据库名' AND TABLE_NAME='表名';
Thanks ~
