如何仅在没有子查询的 UNION ALL 中按一个查询进行排序

Question

我正在使用 UNION ALL 从不相关的数据创建一个列表，以便保存到 SQL Server 2008 中的 Excel。只有 SELECT 语句之一将有一个 ORDER BY，这就是我的问题出现的地方，并显示以下错误消息

'The multi-part identifier "p.Category" could not be bound.'

这是一个简化的工作代码示例，我更喜欢下面的第二个代码示例，但在取消注释第一个 SELECT 查询时中断：

CREATE TABLE #People(Category varchar(50), [Name] varchar(50));

INSERT INTO #People VALUES(1, 'Steve');
INSERT INTO #People VALUES(99, 'Anna');
INSERT INTO #People VALUES(2, 'Sarah'); 

-- Unrelated data SELECT query
--SELECT 'Best Employee' AS Matrix
--     , 'Alan' AS [Name]
--UNION ALL

SELECT CASE
           WHEN p.Category = 1
           THEN 'Very Active'
           WHEN p.Category = 2
           THEN 'Active '
           ELSE 'Departed'
       END AS Matrix
     , p.name AS [Name]
FROM #People p
ORDER BY p.Category;

DROP TABLE #People;

经过一些研究，我发现我可以按以下方式重写查询，这会在这个小示例中给出我想要的结果，但在我的实际情况下我认为不是理想的结果。有没有一种方法可以在不像下面的工作示例那样诉诸子查询的情况下给我正确的结果？

CREATE TABLE #People(Category varchar(50), [Name]  varchar(50));

INSERT INTO #People VALUES(1, 'Steve');
INSERT INTO #People VALUES(99, 'Anna');
INSERT INTO #People VALUES(2, 'Sarah'); 

SELECT *
FROM
(
    -- Unrelated data SELECT query
    SELECT 'Best Employee' AS Matrix
         , 'Alan' AS [Name]
         , '' AS Category

    UNION ALL

    SELECT CASE
               WHEN p.Category = 1
               THEN 'Very Active'
               WHEN p.Category = 2
               THEN 'Active '
               ELSE 'Departed'
           END Matrix
         , p.name AS [Name]
         , p.Category Category
    FROM #People p
) x
ORDER BY x.Category;

DROP TABLE #People;

Answer 1

如果您的问题是您的排序导致 2 个表混淆，您可以添加一列，以便始终首先显示第一个 select 结果集。

CREATE TABLE #People(Category varchar(50), [Name]  varchar(50));

INSERT INTO #People VALUES(1, 'Steve');
INSERT INTO #People VALUES(99, 'Anna');
INSERT INTO #People VALUES(2, 'Sarah'); 

SELECT Matrix, Name, Category
FROM
(
    -- Unrelated data SELECT query
    SELECT 'Best Employee' AS Matrix
         , 'Alan' AS [Name]
         , '' AS Category
         , 1 as Ord

UNION ALL

    SELECT CASE
               WHEN p.Category = 1
               THEN 'Very Active'
               WHEN p.Category = 2
               THEN 'Active '
               ELSE 'Departed'
           END Matrix
         , p.name AS [Name]
         , p.Category Category,
         2 as Ord
    FROM #People p
) x
ORDER BY x.Ord --,Additional Order by columns

Answer 2

ORDER BY 不仅仅适用于一个 SELECT，它适用于整个结果集，适用于所有行 UNIONed 后的整个结果。因此，您需要在 UNION ALL.

的每个 SELECT 中包含将用于排序的列

例如，下面的语法是错误的，因为 ORDER BY 必须在 UNION 的最后一个 SELECT 之后。

SELECT CASE
           WHEN p.Category = 1
           THEN 'Very Active'
           WHEN p.Category = 2
           THEN 'Active '
           ELSE 'Departed'
       END AS Matrix
     , p.name AS [Name]
FROM #People p
ORDER BY p.Category

UNION ALL

SELECT 'Best Employee' AS Matrix
     , 'Alan' AS [Name]

问题中的第二个例子可以写成更简单的形式，没有子查询：

SELECT CASE
           WHEN p.Category = 1
           THEN 'Very Active'
           WHEN p.Category = 2
           THEN 'Active '
           ELSE 'Departed'
       END AS Matrix
     , p.name AS [Name]
     , p.Category
FROM #People p

UNION ALL

SELECT 'Best Employee' AS Matrix
     , 'Alan' AS [Name]
     , NULL AS Category  --- or '' AS Category

ORDER BY Category;

在任何情况下，Category 列都必须添加到 UNION 的每个 SELECT 语句中。我不知道如何避免它。

如何仅在没有子查询的 UNION ALL 中按一个查询进行排序

How to ORDER BY one query only in a UNION ALL without subquery

sql

sql-server

sql-order-by

sql-server-2008

union-all