Question

我有两个选择陈述

1

select Start_Date
    from table1  where Start_Date not in (
    select End_Date
    from table1)

2

 select End_Date from table1
    where End_Date not in (
        select Start_Date
            from table1
        )

我希望在使用union时将不同列中的两个select语句组合在一起它给我一个列，其中包含两个查询的结果，我希望每个查询结果都在不同的列中但是当我使用内部联接时这样

select a.End_Date , b.Start_Date from
( select End_Date from table1
where End_Date not in (
select Start_Date
from table1
) ) a

join

(select Start_Date
from table1 where Start_Date not in (
select End_Date
from table1)
) b
on 1=1

它给我结果每个记录重复四次帮助我下一步做什么??

Answer 1

如果您的每个查询只返回1行，您可以使用：

SELECT 
(select Start_Date
    from table1  where Start_Date not in (
        select End_Date
        from table1)
) AS StartDate,
 (select End_Date from table1
    where End_Date not in (
        select Start_Date
        from table1)
 ) AS EndDate

如果您的查询返回的行数超过1行，则必须选择其他解决方案：

您可以使用UNION：（您将在另一列中将两个查询与“NULL”未对齐）

(select Start_Date, Null AS EndDate
    from table1  where Start_Date not in (
         select End_Date
         from table1)
) 
UNION
(select  Null As StartDate, End_Date 
    from table1
    where End_Date not in (
        select Start_Date
        from table1)
 )

您可以使用JOIN 如果你有一个字段用作“Join On”你可以使用这个字段，如果没有你可以添加一个字段来加入（但你需要检查返回的数据以避免错误）你还要检查什么样的连接可能对你有好处（内 - 左 - rigth）在示例中，我添加了一个要加入的字段并使用内部联接：

SELECT Start_Date, End_Date
FROM
(select 1 as InnerId, Start_Date
    from table1  where Start_Date not in (
        select End_Date
        from table1)
) As Tab1
 INNER JOIN
 (select  1 as InnerId, End_Date from table1
    where End_Date not in (
        select Start_Date
        from table1)
 ) AS Tab2
USING(InnerId)

在两列中合并两个select语句？

1 个答案: