CTE 中的 UNION ALL

Question

我正在尝试让 UNION ALL 与我用于分页的 CTE 一起使用。我需要从两个表中获取与一组条件匹配的所有记录，然后对结果进行分页。第一个表的 CTE 如下所示：

;WITH Results_CTE AS (SELECT t1.SomeIntKey1, ROW_NUMBER() OVER (ORDER BY SomeIntKey1) AS RowNum  
 FROM Table1 t1
 LEFT JOIN CalculatedData d ON d.Key = t1.SomeIntKey1
 WHERE Postcode LIKE 'CHX 1XX%' 
 ) SELECT * FROM Results_CTE a INNER JOIN CalclatedData d ON a.SomeIntKey1 = d.Key WHERE RowNum >= 0 AND RowNum <= 10 OPTION(RECOMPILE) 

第二个表的分页 SQL（工作正常）是：

;WITH Results_CTE AS (SELECT t2.SomeIntKey2, ROW_NUMBER() OVER (ORDER BY SomeIntKey2) AS RowNum  
 FROM Table2 t2
 LEFT JOIN CalculatedData d ON d.Key = t1.SomeIntKey2
 WHERE Postcode LIKE 'CHX 1XX%' 
 ) SELECT * FROM Results_CTE a INNER JOIN CalclatedData d ON a.SomeIntKey2 = d.Key WHERE RowNum >= 0 AND RowNum <= 10 OPTION(RECOMPILE) 

对于合并的分页数据，我尝试过类似的操作：

;WITH Results_CTE AS (SELECT t2.SomeIntKey2, ROW_NUMBER() OVER (ORDER BY SomeIntKey2) AS RowNum  
 FROM Table2 t2
 LEFT JOIN CalculatedData d ON d.Key = t1.SomeIntKey2
 WHERE Postcode LIKE 'CHX 1XX%' 
UNION ALL 
SELECT t1.SomeIntKey1
 FROM Table1 t1
 LEFT JOIN CalculatedData d ON d.Key = t1.SomeIntKey1
 WHERE Postcode LIKE 'CHX 1XX%' 
 ) SELECT * FROM Results_CTE a INNER JOIN CalclatedData d ON a.SomeIntKey2 = d.Key WHERE RowNum >= 0 AND RowNum <= 10 OPTION(RECOMPILE) 

但是，这会导致错误： 使用 UNION、INTERSECT 或 EXCEPT 运算符组合的所有查询在其目标列表中必须具有相同数量的表达式。

我知道 UNION ALL 在最好的情况下可能会令人困惑，尤其是在连接时，但我'我本质上是从两个表中获取 INT 键列表，然后将它们连接到包含我需要的数据的第三个表（两个表中的键将出现在 Data 表的连接列中。

Answer 1

您需要确保两个结果集具有相同的列：

WITH Results_CTE AS
(
    SELECT
        t2.SomeIntKey2 as Key,
        ROW_NUMBER() OVER (ORDER BY SomeIntKey2) AS RowNum  
    FROM
        Table2 t2
    LEFT JOIN CalculatedData d
        ON  d.Key = t1.SomeIntKey2
    WHERE Postcode LIKE 'CHX 1XX%' 
    UNION ALL 
    SELECT
        t1.SomeIntKey1 as Key,
        0 as RowNum
    FROM
        Table1 t1
    LEFT JOIN CalculatedData d
        ON  d.Key = t1.SomeIntKey1
    WHERE Postcode LIKE 'CHX 1XX%' 
 )
 SELECT * FROM Results_CTE a INNER JOIN CalclatedData d ON a.SomeIntKey2 = d.Key
 WHERE RowNum >= 0 AND RowNum <= 10 OPTION(RECOMPILE) 

请注意，UNION ALL 的第二部分现在始终为 RowNum 返回 0。如果您想要 UNION ALL 结果的 RowNum 列，您需要另一个子查询：

WITH Results_CTE AS
(
    SELECT
        s.Key,
        ROW_NUMBER() OVER (ORDER BY s.Key) AS RowNum
    FROM
    (
        SELECT
            t2.SomeIntKey2 as Key,
        FROM
            Table2 t2
            LEFT JOIN CalculatedData d
                ON  d.Key = t1.SomeIntKey2
        WHERE Postcode LIKE 'CHX 1XX%' 
        UNION ALL 
        SELECT
            t1.SomeIntKey1 as Key
        FROM
            Table1 t1
            LEFT JOIN CalculatedData d
                ON  d.Key = t1.SomeIntKey1
        WHERE Postcode LIKE 'CHX 1XX%' 
     )
 )
 SELECT * FROM Results_CTE a INNER JOIN CalclatedData d ON a.SomeIntKey2 = d.Key
 WHERE RowNum >= 0 AND RowNum <= 10 OPTION(RECOMPILE) 

Answer 2

UNION ALL 中的第二个 SELECT 不会返回相同数量的列，因此出现问题。

尝试：

;WITH Results_CTE AS (
  SELECT IntKey, ROW_NUMBER() OVER (ORDER BY IntKey) AS RowNum  
  FROM
  (
     SELECT t2.SomeIntKey2 AS IntKey
     FROM Table2 t2
        LEFT JOIN CalculatedData d ON d.Key = t1.SomeIntKey2
     WHERE Postcode LIKE 'CHX 1XX%' 
     UNION ALL 
     SELECT t1.SomeIntKey1 AS IntKey
     FROM Table1 t1
        LEFT JOIN CalculatedData d ON d.Key = t1.SomeIntKey1
     WHERE Postcode LIKE 'CHX 1XX%' 
  ) t
 ) 
SELECT * FROM Results_CTE a INNER JOIN CalclatedData d ON a.IntKey = d.Key