-
对于SQL的方面，接触的不多，实在有种摸不到头脑的感觉。查看全部
-
MySQL不支持full join：查看全部
-
select a.user_name,b.timestr,b.kills from suer1 a join user_kills b on a.id=b.user_id where user_name='孙悟空' order by b.kills desc limit 2 可以用sql批量查询： select d.user_name,timestr,kills,(select count(*) from user_kills b where b.user_id=a.user_id and a.kills<=b.kills) as cnt from suer_kills a group by user_id.timestr.kills) c join user1 d on c.user_id=d.id where cnt<=2查看全部
-
select a.user_name,b.timestr,b.kills from user1 a join user_kills b on a.id=b.user_id where b.kills=(select max(c.kills) from user_kills where c.user_id = b.user_id) 优化成： select a.user_name,b.timestr,b.kills from user1 a join user_kills b on a.id=b.user_id join user_kills c on c.user_id=b.user_id group by a.user_name,b.timestr,b.kills having b.kills=max(c.kills);查看全部
-
select a.user_name,a.over,(select over from user2 b where a.user_name=b.user_name) as over2 from user1 a 可优化为： select a.user_name,a.over,b.over as over2 from user1 a left join user2 b on a.user_name=b.user_name查看全部
-
SQL语句分类 DDL 数据定义语言，create alter TPL 事务处理语言 DCL 数据控制语言 DML 数据操作语言，insert select update delete查看全部
-
SQL语句分类 DDL 数据定义语言，create alter TPL 事务处理语言 DCL 数据控制语言 DML 数据操作语言，insert select update delete查看全部
-
用来标记一下查看全部
-
分类聚合，在查询多种分类数据时使用到一种聚合方式查看全部
-
left outer Join ：结果集：求出左边表为主，查询与左表相同的数据 语句：select a.user_name,a.over,b.over from user1 a join user2 b on a.user_name=b.user_name where b.user_name is not null查看全部
-
Mysql Full join查看全部
-
inner join查看全部
-
JOIN类型查看全部
-
full join 1查看全部
-
Right Outer Join 3查看全部
举报
0/150
提交
取消