MySQL时间转换/字符串截取/

字符串截取:

SELECT SUBSTRING('abcdefg',2,5)

计算字符长度:

len(string)

--查询2010前入学入学ID
select user from cf_log where substr(user,0,4)<2010 order by user ASC limit 0,10;

统计元组数:

select count(*) from cf_user;

查询重复:

select count(user),user,pwd,name from cf_user group by user having count(user)>1;

查询结果插入表中:

insert into cf_grade1 select * from cf_grade where user='' order by term;

insert into cf_user(user,pwd,name,degree,dept,major,class,year) 
select distinct user,pwd,name,degree,dept,major,class,year from cf_log;

insert into ims_goods_3(model,name,price) select model,name,price 
from ims_goods_5 order by model;

去重:

delete from 表 where ID not in (select max(ID) from 表 group by 重复列);

时间戳转换星期:

--查询星期天的记录
select * from d where DAYOFWEEK(FROM_UNIXTIME(time))=1;

获取当前时间:

select localtime();
select now();
--current_timestamp(),效果一样

获取YYYY-MM-DD日期

select curdate();--2015-09-06

动态时间:

sysdate()

年月日转换:

set @dt = now();
select dayofweek(@dt); -- 1
select dayofmonth(@dt); -- 6
select dayofyear(@dt); -- 249 返回当前年份第多少天

查询指定月份最后一天日期:

select last_day(now()); -- 2015-09-30

select datediff(now(),'2015-08-28');

字符串截取:

SELECT SUBSTRING('abcdefg',2,5)

计算字符长度:

len(string)
--查询2010前入学入学ID
select user from cf_log where substr(user,0,4)<2010 order by user ASC limit 0,10;

查询重复:

select count(user),user,pwd,name from cf_user group by user having count(user)>1;

查询结果插入表中:

insert into cf_grade1 select * from cf_grade where user='' order by term;
insert into cf_user(user,pwd,name,degree,dept,major,class,year) select distinct user,pwd,name,degree,dept,major,class,year from cf_log;

delete from 表 where ID not in (select max(ID) from 表 group by 重复列);

select name,A.user,A.score from (select user,cname,max(score) AS score from cf_grade group by cname) A,cf_user B where A.user=B.user;