我在触发器中创建了一个游标,但它无法正常工作。请帮我解决一下
Create trigger Posts_Raw_To_Queue_Trigger ON SendNotificationPostsRaw FOR INSERT
AS
BEGIN
DECLARE @PostID uniqueidentifier
DECLARE @UserID uniqueidentifier
DECLARE @ProfID int
DECLARE @Email nvarchar(100)
DECLARE @CreationTime datetime
DECLARE @SpecialityID int
SELECT @ProfID= ProfessionalID,@Email= Email from Professionals where UserID=@UserID
SELECT @PostID = I.PostID,@UserID = I.UserID ,@CreationTime =I.CreationTime FROM INSERTED I
DECLARE post_relation_cursor CURSOR FOR select CategoryId from PostCategoryRelations where PostId=@PostID;
OPEN post_relation_cursor;
FETCH NEXT FROM post_relation_cursor INTO @SpecialityID
WHILE @@FETCH_STATUS = 0
BEGIN
INSERT INTO SendNotificationPostsQueue (UserID,PostID,SpecialityID,TemplateID,CreationTime,SendTime,JSONParameters) Values(@UserID,@PostID,1,1,'04/11/2013','04/11/2013','')
FETCH NEXT FROM post_relation_cursor INTO @SpecialityID;
END;
CLOSE post_relation_cursor;
DEALLOCATE post_relation_cursor;
END
如果我删除光标并将虚拟值插入SendNotificationPostsQueue
,它就可以工作。所以我的光标有问题...请告诉我为什么光标不起作用?
答案 0 :(得分:3)
似乎根本不需要使用光标,最好不要在几乎所有情况下都使用光标。只需用标准插件替换扳机的主体(开始和结束之间的部分):
INSERT INTO SendNotificationPostsQueue (UserID,PostID,SpecialityID,TemplateID,CreationTime,SendTime,JSONParameters)
SELECT
i.UserID,
i.PostID,
1,
1,
'04/11/2013', -- Might want i.CreationTime or current_timestamp
'04/11/2013',
''
FROM INSERTED i
-- possibly want "LEFT JOIN Professionals p on i.UserID = p.UserID" here to grab other info
请注意我没有使用只能插入一行的插入的values
子句。我将一个select语句作为插入的一部分,因此插入与select返回的行数。这意味着我们不需要使用游标,也不需要一堆变量来为游标供电。
正如@automatic所提到的,您当前代码的一个问题是您假设INSERTED只保留一行。如果它有多个,那么当您尝试将列分配给变量时,您将抛出错误。
出于优雅,可维护性和性能的原因,我强烈建议您放弃此光标并运行一个简单的插入(因为这就是光标所做的一切)。
答案 1 :(得分:1)
可能存在问题 -
CREATE TRIGGER dbo.Posts_Raw_To_Queue_Trigger
ON SendNotificationPostsRaw
-- for view
INSTEAD OF INSERT
-- OR
-- for table
AFTER INSERT
AS BEGIN
DECLARE
@PostID UNIQUEIDENTIFIER
, @UserID UNIQUEIDENTIFIER
, @ProfID INT
, @Email NVARCHAR(100)
, @CreationTime DATETIME
, @SpecialityID INT
SELECT @ProfID = ProfessionalID
, @Email = Email
FROM Professionals
WHERE UserID = @UserID
-- this posible return invalid result (random record from inserted sequence)
SELECT @PostID = I.PostID
, @UserID = I.UserID
, @CreationTime = I.CreationTime
FROM INSERTED I
DECLARE post_relation_cursor CURSOR LOCAL READ_ONLY FAST_FORWARD FOR
SELECT CategoryID
FROM dbo.PostCategoryRelations
WHERE PostId = @PostID;
OPEN post_relation_cursor;
FETCH NEXT FROM post_relation_cursor INTO @SpecialityID
WHILE @@FETCH_STATUS=0 BEGIN
INSERT INTO SendNotificationPostsQueue (
UserID
, PostID
, SpecialityID
, TemplateID
, CreationTime
, SendTime
, JSONParameters
)
SELECT
@UserID
, @PostID
, @SpecialityID --- !!!
, 1
, '04/11/2013'
, '04/11/2013'
, ''
FETCH NEXT FROM post_relation_cursor INTO @SpecialityID;
END;
CLOSE post_relation_cursor;
DEALLOCATE post_relation_cursor;
END
<强>更新强>
如果我理解正确,那么业务逻辑必须是这样的:
CREATE TRIGGER dbo.Posts_Raw_To_Queue_Trigger
ON dbo.SendNotificationPostsRaw
[INSTEAD OF]/[AFTER] INSERT
AS BEGIN
SET NOCOUNT ON;
DECLARE
@PostID UNIQUEIDENTIFIER
, @UserID UNIQUEIDENTIFIER
, @ProfID INT
, @Email NVARCHAR(100)
, @CreationTime DATETIME
, @SpecialityID INT
DECLARE cur CURSOR LOCAL READ_ONLY FAST_FORWARD FOR
SELECT
i.PostID
, i.UserID
, ProfID = p.ProfessionalID
, p.Email
, i.CreationTime
, pcr.CategoryID
FROM INSERTED i
JOIN dbo.Professionals p ON i.UserID = p.UserID
JOIN dbo.PostCategoryRelations pcr ON i.PostID = pcr.PostID
OPEN cur
FETCH NEXT FROM cur INTO
@PostID
, @UserID
, @ProfID
, @Email
, @CreationTime
, @SpecialityID
WHILE @@FETCH_STATUS = 0 BEGIN
INSERT INTO dbo.SendNotificationPostsQueue
(
UserID
, PostID
, SpecialityID
, TemplateID
, CreationTime
, SendTime
, JSONParameters
)
SELECT
@UserID
, @PostID
, @SpecialityID
, 1
, @CreationTime
, @CreationTime
, ''
FETCH NEXT FROM cur INTO
@PostID
, @UserID
, @ProfID
, @Email
, @CreationTime
, @SpecialityID
END
CLOSE cur
DEALLOCATE cur
END