Mysql 常用SQL语句集锦

** 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';

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Thanks ~

IT小圈儿