Question

   Table 1
    Color
    ------
    Red
    Red
    Blue

    Table 2
    Color
    ------
    Red
    Blue

    Result
    Red (since red in Table 1 2x and only 1x in Table 2)

如何根据表2中的行设计TSQL来删除表1中的行？

换句话说，迭代表2一次，对于每种颜色，从表1中删除一种颜色（不是所有与表2当前颜色相同的颜色）。

Answer 1

只需为每种颜色编号并删除所有数字大于1的所有颜色：

;with cte as(select t1.*, row_number() over(partition by t1.color
                            order by(select null)) as rn
             from table1 t1
             join table2 t2 on t1.color = t2.color)
delete from cte where rn > 1

或改为：

delete from cte where rn = 1

如果您只想为每种颜色删除一行。

Answer 2

DECLARE @Table1 Table (color nvarchar(4))
INSERT INTO @Table1  Values ('Red')
INSERT INTO @Table1  Values ('Red')
INSERT INTO @Table1  Values ('Blue')

DECLARE @Table2 Table (color nvarchar(4))
INSERT INTO @Table2 Values ('Red')
INSERT INTO @Table2  Values ('Blue')

DELETE a
FROM (
SELECT t1.*,
    row_number() OVER (
        PARTITION BY t1.color ORDER BY (SELECT 1)
        ) AS rownum

FROM @Table1 t1
WHERE t1.color IN (
        SELECT t2.color
        FROM @Table2 t2
        )
) a
WHERE a.rownum =1

如果您需要删除重复的颜色，请更改为a.rownum＆gt; 1

根据表2中的行从表1中删除行

2 个答案: