Question

我正在尝试做这样的事情：

SELECT t1.*,
       t2.*
FROM   (SELECT *
        FROM   USER) AS t1,
       (SELECT *
        FROM   t1) AS t2

它在MySQL中不起作用。有可能像以上那样吗？我的另一个选择是获取最后一个子查询并围绕主查询“包装”它。想法？

Answer 1

使用：

SELECT t1.*,
       t2.*
  FROM (SELECT *
          FROM USER) AS t1,
       (SELECT *
          FROM (SELECT *
                  FROM USER) AS t1) AS t2

WITH语法允许您构建在CTE之上：

WITH t1 AS (
  SELECT * FROM USER), -- comma separates them
     t2 AS (
  SELECT * FROM t1)
SELECT t1.*, t2.*
  FROM t1, t2

..但MySQL不支持WITH子句。

Answer 2

为什么不

SELECT t1.*, t2.* FROM USER as t1, USER as t2

？您还应该添加一个条件，否则会产生大量的行。

现在，如果您打算询问如何引用上一个子查询，您应该重复它并添加所需的额外条件：

SELECT t1.*, t2.* FROM (SELECT bar FROM foo WHERE baz=1) as t1, 
(SELECT bluz,bar FROM foo WHERE baz=1 AND quux = 0) as t2 WHERE t2.bar = t1.bar

另一种选择是使用子查询（t1）

创建视图或临时表

Answer 3

如果2个表的列数相同，则可以使用UNION e.g。

SELECT *
FROM   USER
UNION
SELECT *
FROM   t1

如果它们没有相同的列，则需要以某种方式加入表格，例如使用外键。 E.g。

SELECT *
FROM   USER as t1
JOIN   t1 as t2 (on t1.id = t2.id)

Answer 4

我认为您的实际查询要复杂得多。是否有可能创建一个代表子查询的视图，然后你可以使用像Vinko Vrsalovic建议的更简单的选择语句。

查询子查询

4 个答案: