在Teradata中达到QUALIFY ROW_NUMBER

Question

下面是oracle SQL，我想将其更改为Teradata格式。

SELECT branch_code,
    branch_no,
    c_no,
    cd_type
FROM (
    SELECT branch_code,
        branch_no,
        c_no,
        cd_type,
        * * RANK() OVER (
            PARTITION BY c_no ORDER BY cd_type
            ) RANK * *
    FROM (
        SELECT branch_code,
            branch_no,
            c_no,
            MIN(cd_type) cd_type
        FROM EMPLOYEE
        WHERE S_CODE = 'C'
            AND (branch_no) NOT IN (
                SELECT branch_code
                FROM DEPARTMENT
                WHERE branch_code = 'ABC'
                )
        )
    )
WHERE RANK = 1

我已经将QUALIFY用于RANK，如下所示。

SELECT branch_code,
    branch_no,
    c_no,
    cd_type
FROM (
    SELECT branch_code,
        branch_no,
        c_no,
        cd_type,
        * * QUALIFY ROW_NUMBER() OVER (
            PARTITION BY c_no ORDER BY cd_type
            ) * * RANK
    FROM (
        SELECT branch_code,
            branch_no,
            c_no,
            MIN(cd_type) cd_type
        FROM EMPLOYEE
        WHERE S_CODE = 'C'
            AND (branch_no) NOT IN (
                SELECT branch_code
                FROM DEPARTMENT
                WHERE branch_code = 'ABC'
                )
        )
    )
WHERE RANK = 1

但是却收到错误消息“期望在和合格之间。

我们可以在选择语句中放入QUALIFY吗？

Answer 1

通常，在加入和过滤以及GROUP BY和HAVING之后，倒数第二个计算值，例如RANK 。 解析值之后唯一要做的就是ORDER BY 。 这就是为什么在Oracle中，您需要将RANK放入内部查询中，然后在外部查询中测试其值。 在Teradata中， QUALIFY在分析函数之后和ORDER BY之前执行，这意味着您不需要外部查询即可测试RANK值。

我今天没有访问Teradata的权限，因此该查询未经测试，但我想认为它已经接近了：

SELECT branch_code,
    branch_no,
    c_no,
    cd_type
FROM (
    SELECT branch_code,
        branch_no,
        c_no,
        MIN(cd_type) cd_type
    FROM EMPLOYEE
    WHERE S_CODE = 'C'
        AND (branch_no) NOT IN (
            SELECT branch_code
            FROM DEPARTMENT
            WHERE branch_code = 'ABC'
        )
)
QUALIFY ROW_NUMBER() OVER (PARTITION BY c_no ORDER BY cd_type) = 1

Answer 2

您可能简化了现有查询，因为这不是有效的Oracle SQL（内联视图中没有GROUP BY）。 另外，您可以在NOT IN branch_no与branch_code进行比较。

否则，Ed Gibbs的答案可以进一步简化为：

SELECT branch_code,
    branch_no,
    c_no,
    MIN(cd_type) cd_type
FROM EMPLOYEE
WHERE S_CODE = 'C'
    AND (branch_no) NOT IN (
        SELECT branch_no
        FROM DEPARTMENT
        WHERE branch_code = 'ABC'
        )
GROUP BY branch_code,
    branch_no,
    c_no
QUALIFY
   RANK()
   OVER (PARTITION BY c_no 
         ORDER BY MIN(cd_type) = 1

如果branch_no被定义为NULLable，则还应该将NOT IN重写为NOT EXISTS