Question

select t1.table1 from table1 as t1
where t1.column1 
in 
(
    select t2.column2 from table2 as t2 
    join 
    table3 as t3  on t2.column1=t3.column1 
    where t3.columnx=5
);

上面是我正在解雇的mysql查询。从子查询表中也想要一些数据。

例如说表t2中的columnxy。

失败的查询

select t1.table1,t2.columnxy from table1 as t1
where t1.column1 
in 
(
    select t2.column2 from table2 as t2 
    join 
    table3 as t3  on t2.column1=t3.column1 
    where t3.columnx=5
);

如果我用选择外部查询添加它们会给出错误“未知列”，这确实有意义。

是正确的方法还是应该用连接重写查询？

Answer 1

使用连接重写查询：

SELECT t1.table1, t.columnxy
FROM   table1 AS t1 JOIN (
  SELECT t2.column2, t2.columnxy
  FROM   table2 AS t2 JOIN table3 AS t3 USING (column1)
  WHERE  t3.columnx = 5
) t ON t1.column1 = t.column2

或者：

SELECT t1.table1, t2.columnxy
FROM   table1 AS t1
  JOIN table2 AS t2 ON t1.column1 = t2.column2
  JOIN table3 AS t3 ON t2.column1 = t3.column1
WHERE  t3.columnx = 5

Answer 2

此时t2不可用。您应该使用联接。使用t1.column1 = t2.column2应该这样做。

从子查询mysql中选择数据

2 个答案: