UNION ALL on 2 tables select with Cases

Question

我是运行 SQL Server 2005。我有 2 个 table 具有相同的列，但保存的数据却截然不同。

SELECT *
FROM Table1 
WHERE ItemID IN ('4','2','1') 
ORDER BY 
    CASE  WHEN ItemID = 4 then 1 WHEN ItemID = 2 then 2 WHEN ItemID = 1 then 3 END 
UNION ALL 
SELECT * 
FROM Table2 
WHERE ItemID IN ('3','1','5','2') 
ORDER BY 
    CASE  WHEN ItemID = 3 then 4 WHEN ItemID = 1 then 5 WHEN ItemID = 5 then 6 WHEN ItemID = 2 then 7 END

我需要保持 ItemID 的顺序与它们被选中的顺序一致，这就是我使用 CASE 的原因。这一切在每个 table 上都可以正常工作，但我找不到一种方法将它们组合成 1 table 结果与每个 table 订购的结果。

即

4 (Table1)
2 (Table1)
1 (Table1)
3 (Table2)
1 (Table2)
5 (Table2)
2 (Table2)

非常感谢所有帮助。

Answer 1

试试这个：

SELECT *
FROM (
    SELECT * , 1 as ord
    FROM Table1 
    WHERE ItemID IN (4, 2, 1) 
  UNION ALL 
    SELECT * , 2 as ord
    FROM Table2 
    WHERE ItemID IN (3, 1, 5, 2) ) t
ORDER BY  
    ord,
    CASE  WHEN ItemID = 3 then 4 WHEN ItemID = 1 then 5 WHEN ItemID = 5 then 6 WHEN ItemID = 2 then 7 END,
    CASE  WHEN ItemID = 4 then 1 WHEN ItemID = 2 then 2 WHEN ItemID = 1 then 3 END

或

SELECT *,
    ROW_NUMBER() OVER (ORDER BY ord,
        CASE  WHEN ItemID = 3 then 4 WHEN ItemID = 1 then 5 WHEN ItemID = 5 then 6 WHEN ItemID = 2 then 7 END,
        CASE  WHEN ItemID = 4 then 1 WHEN ItemID = 2 then 2 WHEN ItemID = 1 then 3 END) as RowNo 

FROM (
    SELECT * , 1 as ord
    FROM Table1 
    WHERE ItemID IN (4, 2, 1) 
  UNION ALL 
    SELECT * , 2 as ord
    FROM Table2 
    WHERE ItemID IN (3, 1, 5, 2) ) t

Answer 2

您可以使用以下查询：

SELECT Table1.* , x.[Order] AS Ord
FROM Table1 
CROSS APPLY (SELECT CASE ItemID
                       WHEN 4 THEN 1 
                       WHEN 2 THEN 2 
                       WHEN 1 THEN 3 
             END) x([Order])  
WHERE ItemID IN ('4','2','1') 

UNION ALL 

SELECT Table2.* , y.[Order] AS Ord
FROM Table2 
CROSS APPLY (SELECT CASE ItemID 
                       WHEN 3 THEN 4 
                       WHEN 1 THEN 5 
                       WHEN 5 THEN 6 
                       WHEN 2 THEN 7 
                    END) y([Order])
WHERE ItemID IN ('3','1','5','2')
ORDER BY Ord

计算字段 [Order] 保证来自 Table1 的记录首先出现，然后是 Table2 的记录。它还确保在每个 Table1 或 Table2 分区内进行排序。

Demo here

这是不使用 CROSS APPLY 的替代语法：

SELECT Table1.*, 
       CASE ItemID
          WHEN 4 THEN 1 
          WHEN 2 THEN 2 
          WHEN 1 THEN 3 
       END AS Ord
FROM Table1 
WHERE ItemID IN ('4','2','1') 

UNION ALL 

SELECT Table2.*, 
       CASE ItemID 
          WHEN 3 THEN 4 
          WHEN 1 THEN 5 
          WHEN 5 THEN 6 
          WHEN 2 THEN 7 
       END AS Ord
FROM Table2 
WHERE ItemID IN ('3','1','5','2')
ORDER BY Ord

Demo here

UNION ALL on 2 tables select with Cases

UNION ALL on 2 tables select with Cases

sql

sql-server

sql-server-2005

union-all