即使没有数据，也强制查询返回所有范围答案

【问题标题】：Force query to return all ranges even when there is no data即使没有数据，也强制查询返回所有范围
【发布时间】：2019-03-18 01:26:30
【问题描述】：

我有一个查询，它计算 3 个总和，然后将其分类为后期付款范围。

但有时某些范围没有数据，因此查询返回的行数少于 3 行。

即使没有特定 DaysLate 范围的数据，如何强制查询始终返回 3 行？在这种情况下，Suma 和 Docs 应包含零。

SELECT MIN(b.Range) Nazwa, SUM(b.Remaining) Suma, COUNT(*) Docs
FROM (
SELECT
CASE
    WHEN a.DaysLate BETWEEN 1 AND 14 THEN 'Late 1 to 14 days'
    WHEN a.DaysLate BETWEEN 15 AND 30 THEN 'Late 15 to 30 day'
    ELSE 'Late over 30 days'
END AS Range,
CASE
    WHEN a.DaysLate BETWEEN 1 AND 14 THEN 1
    WHEN a.DaysLate BETWEEN 15 AND 30 THEN 2
    ELSE 3
END AS Order,
Remaining, DaysLate
FROM (
    SELECT DATEDIFF(dd, PaymentDate, GETDATE()) DaysLate, (WN - MA) Remaining
    FROM dbo.MyData
    WHERE DATEDIFF(dd, PaymentDate, GETDATE()) > 0 AND KOD_ID = @KOD_ID
    ) a
) b
GROUP BY b.Order
ORDER BY b.Order ASC

【问题讨论】：

标签： sql tsql case

【解决方案1】：

您需要LEFT JOIN，但您也可以使用APPLY 简化查询：

SELECT ranges.range, SUM(v.Remaining) as Suma,
       COUNT(*) as Docs
FROM (VALUES ('Late 1 to 14 days', 1),
             ('Late 15 to 30 day', 2),
             ('Late over 30 days', 3)
     ) ranges(range, ord) LEFT JOIN
     (dbo.MyData d CROSS APPLY
      (VALUES (DATEDIFF(day, d.PaymentDate, GETDATE()),
               WN - MA
              )
      ) v(DaysLate, Remaining) CROSS APPLY
      (VALUES (CASE WHEN v.DaysLate BETWEEN 1 AND 14
                    THEN 'Late 1 to 14 days'
                    WHEN v.DaysLate BETWEEN 15 AND 30
                    THEN 'Late 15 to 30 day'
                    ELSE 'Late over 30 days'
               END)
      ) v1(range)
     )
     ON v1.range = ranges.range                  
WHERE v.DaysLate > 0 AND
      KOD_ID = @KOD_ID
GROUP BY v.range, v.ord
ORDER BY v.ord;

【讨论】：