Question

我有3个SQL语句，我想创建一个视图并返回3列，每列代表一个计数。

以下是我的陈述

SELECT Count(*) 
FROM PlaceEvents 
WHERE PlaceID = {placeID} AND EndDateTimeUTC >= GETUTCDATE()

SELECT Count(*) 
FROM PlaceAnnouncements 
WHERE PlaceID = {placeID}

SELECT Count(*) 
FROM PlaceFeedback 
WHERE PlaceID = {placeID} AND IsSystem = 0

我知道如何创建一个基本视图但是如何创建一个允许我将这3个列placeID作为用于过滤的列

的视图

我想执行以下操作以返回正确的数据

SELECT * 
FROM vMyCountView 
WHERE PlaceID = 1

CREATE VIEW vMyCountView AS
  (...) AS ActiveEvents,
  (...) AS Announcements,
  (...) AS UserFeedback,
  PlaceID

Answer 1

我宁愿使用一个函数，然后使用一个视图：

这允许您传入您喜欢的任何参数（我假设placeId是INT）并在您的查询中处理它。处理非常简单，只需使用View：

Name: ABC,
Department: Technical
Salary: 1000

Name: XYZ
Department: Technical
Salary:  1200

Name: PQR
Department: Technical
Salary: 1600

这就是你怎么称呼它。您可以将其用于CREATE FUNCTION MyCountFunction(@PlaceID INT) RETURNS TABLE AS RETURN SELECT (SELECT Count(*) FROM PlaceEvents WHERE PlaceID = @PlaceID AND EndDateTimeUTC >= GETUTCDATE()) AS ActiveEvents ,(SELECT Count(*) FROM PlaceAnnouncements WHERE PlaceID = @PlaceID) AS Announcements ,(SELECT Count(*) FROM PlaceFeedback WHERE PlaceID = @PlaceID AND IsSystem = 0) AS UserFeedback ,@PlaceID AS PlaceID; GO s或JOIN也...

APPLY

Answer 2

您可以将它们组合为多个选择子查询。

CREATE VIEW vMyCountView AS
SELECT
(SELECT Count(*) FROM PlaceEvents 
 WHERE PlaceID = s.placeID AND EndDateTimeUTC >= GETUTCDATE()) AS ActiveEvents,
(SELECT Count(*) FROM PlaceAnnouncements 
 WHERE PlaceID = s.placeID) AS Announcements,
(SELECT Count(*) FROM PlaceFeedback 
 WHERE PlaceID = s.placeID AND IsSystem = 0) AS UserFeedback,
 placeID
from Sometable s

Answer 3

根据定义，view是一个select语句。如果对您的业务逻辑有意义，则可以使用join，union等提供 create view是批量中唯一的查询。

Answer 4

您可以使用GROUP BY创建类似的视图：

SELECT
    PlaceId
,   Count(peId) AS ActiveEvents
,   COUNT(paId) AS Announcements
,   COUNT(fbId) AS UserFeedback
FROM (
    SELECT PlaceId, 1 AS peId, NULL AS paId, NULL AS fbId
    FROM PlaceEvents
    WHERE EndDateTimeUTC >= GETUTCDATE()
UNION ALL
    SELECT PlaceId, NULL AS peId, 1 AS paId, NULL AS fbId
    FROM PlaceAnnouncements
UNION ALL
    SELECT PlaceId, NULL AS peId, NULL AS paId, 1 AS fbId
    FROM PlaceFeedback
    WHERE IsSystem = 0
) src
GROUP BY PlaceId

这个选择背后的想法，很容易进入视图，是从三个表中选择一个项目进行计数，然后将它们全部分组。

如果你有两个活动事件，一个公告和三个地方ID 123的反馈，那么三个内部选择将产生这个：

PlaceId  peId  paId  fbId
-------  ----  ----  ----
    123     1  NULL  NULL
    123     1  NULL  NULL
    123  NULL     1  NULL
    123  NULL  NULL     1
    123  NULL  NULL     1
    123  NULL  NULL     1

3陈述成一种观点

4 个答案: