在 sql 服务器的视图中组合多个 UNION

Question

我想创建如下视图。

Create view SomeView
AS
SELECT DISTINCT ISNULL(ID,'ID') as Id, 
ISNULL(ID,'unknown') + ':' + 'ID' AS label,
ISNULL(ID,'unknown') AS [value]
FROM [test].[emp].[OrgView]
  UNION
SELECT DISTINCT ISNULL(EMP_ID,'ID') as Id, 
ISNULL(EMP_ID,'unknown') + ':' + 'EMP_ID' AS label,
ISNULL(EMP_ID,'unknown') AS [value]
FROM [test].[emp].[OrgView]
  UNION
SELECT DISTINCT ISNULL(LICENSE_NO,'LICENSE_NO') as Id, 
ISNULL(LICENSE_NO,'unknown') + ':' + 'LICENSE_NO' AS label,
ISNULL(LICENSE_NO,'unknown') AS [value]
FROM [test].[emp].[OrgView]
.
.
.
.
.
10 such selects

所以在这种情况下，是为每个 select 块调用一次还是只调用一次？ 我不希望每个 select 进行 10 次不同的调用。如果你知道，请给我指出一些在线资源。

Answer 1

逆轴使用 APPLY:

SELECT DISTINCT COALESCE(v.ID, v.id_default) as Id, 
       COALESCE(o.FIRST_NAME, 'unknown') + ':' + v.name_suffix AS label,
       COALESCE(o.VALUE, 'unknown') AS [value]
FROM [test].[emp].[OrgView] o CROSS APPLY
     (VALUES (o.ID, 'ID', 'Unknown'),
             (o.EMP_ID, 'ID', 'EMP'),
             (o.LICENSE, 'LICENSE_NO', 'LICENSE_NO'), . . . 
     ) v(ID, id_default, name_suffix);

在 sql 服务器的视图中组合多个 UNION

combining multiple UNION inside a view in sql server

sql

sql-server

sql-tuning