sql - 根据其他列的值优化具有不同列计数的查询

Question

必须有更好的方法来写这个，但我只是不确定那是什么。基本上，我试图从一列中计算不同的值，其中在单独的列中满足条件。我找到了这个链接，但不知道如何在这里应用它。

这是查询，我使用的是 SQL Server 2008R2

SELECT lot,
    (SELECT COUNT(DISTINCT d.pid) FROM invdet d WHERE upk = 0 and d.lot = [invdet].lot) as noUpk,
    (SELECT COUNT(DISTINCT d.pid) FROM invdet d WHERE upk = 1 and d.lot = [invdet].lot) as isUpk
FROM invdet
WHERE ([status] in ('PQ','P2','FA','F2','BH','RL','SC','LD','PS'))
GROUP BY lot
HAVING COUNT(CASE WHEN invdet.upk = 1 THEN 1 ELSE null END) > 0

Answer 1

COUNT DISTINCT您可以利用不计入 NULL的事实对您有利。为了检查所有行，创建一个WHERE EXISTS子句而不是将结果集限制为这些状态：

SELECT lot,
    COUNT(DISTINCT (CASE WHEN upk = 0 THEN pid ELSE NULL END)) as noUpk
    COUNT(DISTINCT (CASE WHEN upk = 1 THEN pid ELSE NULL END)) as isUpk
FROM invdet q
WHERE EXISTS
(
    SELECT 1 
    FROM invdet i 
    WHERE i.[status] in ('PQ','P2','FA','F2','BH','RL','SC','LD','PS')
    AND i.lot = q.lot
)
GROUP BY lot
HAVING COUNT(CASE WHEN upk = 1 THEN 1 ELSE null END) > 0

---

您还可以有效地将HAVING子句移动到WHERE EXISTS子句中，这可能会更快，从而导致：

SELECT lot,
    COUNT(DISTINCT (CASE WHEN upk = 0 THEN pid ELSE NULL END)) as noUpk
    COUNT(DISTINCT (CASE WHEN upk = 1 THEN pid ELSE NULL END)) as isUpk
FROM invdet q
WHERE EXISTS
(
    SELECT 1 
    FROM invdet i 
    WHERE i.[status] in ('PQ','P2','FA','F2','BH','RL','SC','LD','PS')
    AND i.lot = q.lot
)
WHERE EXISTS
(
    SELECT 1 
    FROM invdet i 
    WHERE i.upk = 1 
    AND i.lot = q.lot
)
GROUP BY lot