在查询中使用'as'

Question

我有一个这样的表，类型是innodb，id和sid被编入索引。

  id | sid
  ##########
   1 | 100
   1 | 101
   1 | 102
   1 | 103
   1 | 104
   1 | 105
   2 | 100
   2 | 101
   3 | 100
   3 | 101

我需要id有sid 100，... 105喜欢id = 1。 我有这个查询

select t1.id
  from test as t1, test as t2, test as t3,
       test as t4, test as t5, test as t6
 where t1.sid=100
   and t2.sid=101
   and t3.sid=102
   and t4.sid=103
   and t5.sid=104
   and t6.sid=105
   and t1.id = t2.id = t3.id = t4.id = t5.id = t6.id

但是当我运行查询时，phpmyadmin会挂起。 记录数量为2000。

什么是优化查询？

Answer 1

令人惊讶的是，显示的SQL语句编译/运行。

但是，您可以通过重写当前最后一行来拯救它：

select t1.id
  from test as t1, test as t2, test as t3,
       test as t4, test as t5, test as t6
 where t1.sid = 100
   and t2.sid = 101
   and t3.sid = 102
   and t4.sid = 103
   and t5.sid = 104
   and t6.sid = 105
   and t1.id = t2.id
   and t1.id = t3.id
   and t1.id = t4.id
   and t1.id = t5.id
   and t1.id = t6.id;

---

  

此查询是否最佳？

鉴于您对Maulik Vora的答案的评论，范围{100 .. 105}只是一个例子，那么我们需要知道它是否总是6个值，或者它是5还是7或其他数字。但是，最佳结构可能使用临时表（称为ListToMatch，其中包含非空唯一列SID），其中包含所需的任何值，并且查询为：

SELECT T.ID
  FROM Test AS T JOIN ListToMatch AS L ON T.SID = L.SID
 GROUP BY T.ID
 HAVING COUNT(*) = (SELECT COUNT(*) FROM ListToMatch);

将您感兴趣的值集插入ListToMatch;然后，您可以获取匹配的ID值列表。这可能更接近最优，尤其是因为它可以像对6那样轻松地适应1值和100值，而用100路自连接重写SQL并没有太多考虑。

Answer 2

select t2.id from (select id, max(sid) as mxsid, min(sid) as mnsid from test
group by id having count(id) = 6) as t2 
where t2.mxsid = 105 and t2.mnsid = 100