MySQL 常用查詢

1、

select uuid();

select now();
set @schoolid = '1234567890123456789';
select * sys_user_info where mobile is null
select * sys_user_info where mobile is not null
set @adminid = '';
select @adminid := id from sys_user_info where mobile = 'admin';
-- 時間格式化
select date_format(capture_time, '%y-%m-%d'),`inout`,student_id 
from trans_student_inout 
where date_format(created_time, '%y-%m-%d')='2019-08-01';
group by date_format(capture_time, '%y-%m-%d'),`inout`,student_id;
-- 時間格式化
select * from sys_user_info where date_format(created_time, '%y-%m-%d') = '2019-08-01';

函式：concat(str1,str2,…)

描述：字串 s1,s2 等多個字串合併為乙個字串；合併多個字串；

注意：如有任何乙個引數為null ，則返回值為 null；

例項

select concat("sql ", "runoob ", "gooogle ", "facebook") as concatenatedstring;

set @ex123 = '\'123',\'456\'';

set @sql123 = concat('select * from sys_user_info where user_name in (',@ex123,')');
select @sql123;

5、6、

7、8、

9、0、

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