需要帮助来简化此 T-SQL 查询

Question

我有这个有效的 T-SQL 查询，有什么方法可以简化它吗？

SELECT COUNT(*) FROM Tablename 是重复的，只是每个查询的条件不同，那么有没有办法进一步简化呢？谢谢

SELECT COUNT(*) FROM Table 
WHERE columnA = 'I' AND columnB = 'I' AND columnC =''

UNION ALL

SELECT COUNT(*) FROM Table 
WHERE columnA = 'I' AND columnB = 'I' AND columnC <>''

UNION ALL

SELECT COUNT(*) FROM Table
WHERE columnA IN ('A','R') AND columnB = 'I' AND columnD IN (SELECT columnE FROM Table2)

UNION ALL

SELECT COUNT(*) FROM Table 
WHERE columnA IN ('B') AND columnB = 'I'

UNION ALL

SELECT COUNT(*) FROM Table 
WHERE columnA IN ('R') AND columnB = 'S'

UNION ALL

SELECT COUNT(*) FROM Table 
WHERE columnA IN ('A') AND columnB = 'S'

这是工作查询，我的输出是 6 行，想要保持它

Answer 1

让我假设BI_BRH 在STDHOST 中是唯一的。这不是绝对必要的，但它正在简化。

然后你可以使用条件聚合。我认为将值放在列中是最简单的方法：

SELECT SUM(CASE WHEN STATUS = 'I' AND TRX_STATE = 'I' AND ASSIGN_TO = '' THEN 1 ELSE 0 END),
       SUM(CASE WHEN STATUS = 'I' AND TRX_STATE = 'I' AND ASSIGN_TO <>'' THEN 1 ELSE 0 END)
       SUM(CASE WHEN STATUS IN ('A','R') AND TRX_STATE = 'I' AND s.BI_BRH IS NOT NULL THEN 1 ELSE 0 END)
       SUM(CASE WHEN STATUS IN ('B') AND TRX_STATE = 'I' THEN 1 ELSE 0 END)
       SUM(CASE WHEN STATUS IN ('R') AND TRX_STATE = 'S' THEN 1 ELSE 0 END)
       SUM(CASE WHEN STATUS IN ('A') AND TRX_STATE = 'S' THEN 1 ELSE 0 END)
FROM ICSCHQINFO i LEFT JOIN
     STDHOST s
     ON s.BI_BRH = i.BRH_ASSIGN_TO;

Answer 2

您的代码在同一个表上运行 6 次，在 WHERE 子句中使用不同的条件并返回 6 行。

假设您拥有的 6 个条件是互斥的，您可以创建一个 CTE，为每一行返回它所属的类别，然后在该类别上聚合：

WITH cte AS (
  SELECT CASE 
           WHEN STATUS = 'I' AND TRX_STATE = 'I' AND ASSIGN_TO = '' THEN 'cat1'
           WHEN STATUS = 'I' AND TRX_STATE = 'I' AND ASSIGN_TO <> '' THEN 'cat2'
           WHEN STATUS IN ('A','R') AND TRX_STATE = 'I' AND BRH_ASSIGN_TO IN (SELECT BI_BRH FROM STDHOST) THEN 'cat3'
           WHEN STATUS IN ('B') AND TRX_STATE = 'I' THEN 'cat4'
           WHEN STATUS IN ('R') AND TRX_STATE = 'S' THEN 'cat5'
           WHEN STATUS IN ('A') AND TRX_STATE = 'S' THEN 'cat6'
         END category
  FROM ICSCHQINFO          
)
SELECT category, COUNT(*) counter
FROM cte
GROUP BY category

如果没有任何类别的行，并且在这种情况下您想要一个带有 0 的行，您需要另一个 CTE 来返回类别并将 LEFT 加入到另一个 CTE：

WITH 
  categories AS (SELECT category FROM (VALUES ('cat1'), ('cat2'), ('cat3'), ('cat4'), ('cat5'), ('cat6')) v(category)),
  cte AS (
    SELECT CASE 
             WHEN STATUS = 'I' AND TRX_STATE = 'I' AND ASSIGN_TO = '' THEN 'cat1'
             WHEN STATUS = 'I' AND TRX_STATE = 'I' AND ASSIGN_TO <> '' THEN 'cat2'
             WHEN STATUS IN ('A','R') AND TRX_STATE = 'I' AND BRH_ASSIGN_TO IN (SELECT BI_BRH FROM STDHOST) THEN 'cat3'
             WHEN STATUS IN ('B') AND TRX_STATE = 'I' THEN 'cat4'
             WHEN STATUS IN ('R') AND TRX_STATE = 'S' THEN 'cat5'
             WHEN STATUS IN ('A') AND TRX_STATE = 'S' THEN 'cat6'
           END category
    FROM ICSCHQINFO          
  )
SELECT c.category, COUNT(t.category) counter
FROM categories c LEFT JOIN cte t
ON t.category = c.category
GROUP BY c.category