Question

我想在我的sql数据库中检索第二个10个UNIQUE行，为了选择第二个10行，我使用下一个脚本：

SELECT col1, col2 FROM (
    SELECT col1, col2, ROW_NUMBER() OVER (ORDER BY ID) AS RowNum
    FROM MyTable
) AS MyDerivedTable WHERE MyDerivedTable.RowNum BETWEEN 10 AND 19

但是现在我想在该集合中使用UNIQUE行，当我在下一个示例中使用DISTINCT时，DISTINCT也会超过RowNum，这会使每一行成为DISTINCT行。 ..如何从RowNum中排除DISTINCT？

SELECT col1, col2 FROM (
    SELECT DISTINCT col1, col2, ROW_NUMBER() OVER (ORDER BY ID) AS RowNum
    FROM MyTable
) AS MyDerivedTable WHERE MyDerivedTable.RowNum BETWEEN 10 AND 19

Answer 1

您需要使用group by而不是distinct，因为它们会在查询执行的不同时刻应用。当然，由于col1和col2与ID处于N：1关系，因此您需要告诉SQL在编号行时要使用哪个ID。这可能是MAX(ID)。所以：

SELECT col1, col2 FROM (
    SELECT col1, col2, ROW_NUMBER() OVER (ORDER BY MAX(ID)) AS RowNum
    FROM MyTable
    GROUP BY col1, col2
) AS MyDerivedTable WHERE MyDerivedTable.RowNum BETWEEN 10 AND 19

Answer 2

如果你想在结果中区分这10行，你可以在Select子句外进行：

SELECT DISTINCT col1, col2 FROM (
    SELECT col1, col2, ROW_NUMBER() OVER (ORDER BY ID) AS RowNum
    FROM MyTable
) AS MyDerivedTable WHERE MyDerivedTable.RowNum BETWEEN 10 AND 19

此外，如果您使用SQL Server 2012，则可以使用新的甜蜜语句OFFSET FETCH：

   SELECT DISTINCT col1, col2 FROM (
        SELECT col1, col2
        FROM MyTable
        ORDER BY ID
        OFFSET 10 ROWS FETCH FIRST 10 ROWS ONLY
    ) AS MyDerivedTable

Answer 3

SELECT DISTINCT col1, col2 
FROM MyTable
ORDER BY ID
LIMIT 10, 19

在SQL中检索第二个10个UNIQUE行

3 个答案: