Question

我正在使用UNION ALL编写4个查询，并按字段1对它们进行排序。

SELECT Field1,Field2,Field3,Field4
FROM table1 

UNION ALL

SELECT Field1,Field2,Field3,Field4
FROM table2 

UNION ALL


SELECT Field1,Field2,Field3,Field4
FROM table3 

UNION ALL

SELECT Field1,Field2,Field3,Field4
FROM table4 

ORDER BY Field1

我想仅返回field1出现两次的行。

任何帮助将不胜感激

Answer 1

SELECT Field1, Field2, Field3, Field4, count(*) from (
    ... your query ...
)
GROUP BY Field1, Field2, Field3, Field4
HAVING count(*)=2

（这是Oracle语法，我希望这也适用于sql server）。

或者，如果您想要Field1出现两次的所有行，但Field2，Field3和Field4可能相同或可能不同：

SELECT Field1, Field2, Field3, Field4 from (
    ... your query ...
) where Field1 in (
    SELECT Field1 from (
        SELECT Field1, count(*) from (
            ... your query ...
        )
        GROUP BY Field1
        HAVING count(*) = 2
    )
)

（再次使用Oracle语法）。

SQL - 从UNION ALL查询中选择Duplicates

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