Here is a trigger
CREATE TRIGGER [dbo].[CheckApplyId]
ON [dbo].[AppliedStudent_event] INSTEAD OF INSERT
AS
DECLARE #studentId INT
DECLARE #compReq_Id INT
BEGIN
SELECT #studentId = studentId
FROM INSERTED
SELECT #compReq_Id = compReq_Id
FROM INSERTED
IF EXISTS(SELECT StudentId,
compreq_id
FROM AppliedStudent_event
WHERE StudentId = #studentId
AND compreq_id = #compReq_Id)
BEGIN
ROLLBACK
PRINT 'User Already Applied'
END
END
When in insert a data into a table using command:
INSERT INTO AppliedStudent_event (StudentId, compreq_id)
VALUES (3026, 1)
Message is:
(1 row(s) affected)
But when I execute a sql command no data is inserted in the table.
Can you please tell why are you using trigger because you use only assign the variable #studentId and #compReq_Id from inserted table.
That's a broken trigger because inserted can contain multiple (or no) rows - so a statement like SELECT #ScalarVariable = column from inserted is always wrong.
And it's unnecessary since you can just place a UNIQUE constraint on the StudentId and compreq_id columns:
ALTER TABLE AppliedStudent_event
ADD CONSTRAINT UQ_Student_Events
UNIQUE (StudentId,compreq_id)
And it's further broken because you've specified it as an instead of trigger - that says that your code is going to be responsible for the actual insert - but your code doesn't actually do that. That's why no data ends up in the table.
If you insist on doing it as a trigger, it's actually tricky to get everything correct (that's why I'd really recommend the UNIQUE constraint). It'll end up being something like this:
CREATE TRIGGER [dbo].[CheckApplyId]
ON [dbo].[AppliedStudent_event] INSTEAD OF INSERT
AS
IF EXISTS(select
StudentId,compreq_id,COUNT(*)
from inserted
group by StudentId,compreq_id
HAVING COUNT(*) > 1)
OR EXISTS (select *
from inserted i
inner join
AppliedStudent_event e
on
i.StudentId = e.StudentId and
i.compreq_id = e.compreq_id)
BEGIN
ROLLBACK
PRINT 'User Already Applied'
END
ELSE
BEGIN
INSERT INTO AppliedStudent_event(StudentId,compreq_id /* Other columns? */)
SELECT StudentId,compreq_id /* And again, other columns */
FROM inserted
END
Related
I can detect duplicate records, but when I'm inserting new data it will detect it as a duplicate record even if doesn't already exist.
Here is my code:
ALTER TRIGGER [dbo].[SDPRawInventory_Dup_Trigger]
ON [dbo].[SDPRawInventory]
AFTER INSERT
AS
DECLARE #Year float,
#Month float,
#SDPGroup nvarchar(255);
SELECT
#Year = i.InvYear, #Month = i.InvMonth, #SDPGroup = i.SDPGroup
FROM inserted i;
IF (SELECT COUNT(*) FROM SDPRawInventory A
WHERE A.InvYear = #Year
AND A.InvMonth = #Month
AND A.SDPGroup = #SDPGroup) >= 1
BEGIN
RAISERROR ('Duplicate data', 16, 1)
ROLLBACK;
END
ELSE
BEGIN
INSERT INTO SDPRawInventory
SELECT * FROM inserted;
END
This is the table
And to clarify there is no primary key nor unique identifier.
If you are unable to put a constraint in place, then you need to handle the fact that Inserted may have multiple records. And because its an after insert trigger, you don't need to do anything if no duplicates are found because the records are already inserted.
ALTER TRIGGER [dbo].[SDPRawInventory_Dup_Trigger]
ON [dbo].[SDPRawInventory]
AFTER INSERT
AS
BEGIN
SET NOCOUNT ON;
IF EXISTS (
SELECT 1
FROM dbo.SDPRawInventory S
INNER JOIN Inserted I ON
-- Test for a duplicate
S.InvYear = I.InvYear
AND S.InvMonth = I.InvMonth
AND S.SDPGroup = I.SDPGroup
-- But ensure the duplicate is a *different* record - assumes a unique ID
AND S.ID <> I.ID
)
BEGIN
THROW 51000, 'Duplicate data.', 1;
END;
END;
Note the simplified and modern error handling.
EDIT: And if you have no unique key, and no permission to add one, then you need an instead of trigger to only insert non-duplicates e.g.
ALTER TRIGGER [dbo].[SDPRawInventory_Dup_Trigger]
ON [dbo].[SDPRawInventory]
INSTEAD OF INSERT
AS
BEGIN
SET NOCOUNT ON;
-- Reject the entire insert if a single duplicate exists
-- Note if multiple records are inserted, some of which are duplicates and some of which aren't, they all get rejected
IF EXISTS (
SELECT 1
FROM dbo.SDPRawInventory S
INNER JOIN Inserted I ON
-- Test for a duplicate
A.InvYear = I.InvYear
AND A.InvMonth = I.InvMonth
AND A.SDPGroup = I.#SDPGroup
)
-- Test that Inserted itself doesn't contain duplicates
OR EXISTS (SELECT 1 FROM Inserted GROUP BY InvYear, InvMonth, SDPGroup HAVING COUNT(*) > 1)
BEGIN
THROW 51000, 'Duplicate data.', 1;
END;
INSERT INTO dbo.SDPRawInventory (SDP_SKU_DESC, WholeQty, InvYear, InvMonth, SDPGroup, invUOM, LooseQty)
SELECT SDP_SKU_DESC, WholeQty, InvYear, InvMonth, SDPGroup, invUOM, LooseQty
FROM Inserted I
WHERE NOT EXISTS (
SELECT 1
FROM dbo.SDPRawInventory S
-- Test for a duplicate
WHERE S.InvYear = I.InvYear
AND S.InvMonth = I.InvMonth
AND S.SDPGroup = I.SDPGroup
);
END;
Note: This doesn't do anything to handle existing duplicates.
This trigger is executed after the new records were inserted, so it will at least find the original records in the SELECT COUNT statement. Changing >= 1 into >= 2 can only partially fix this when inserting is guaranteed to occur one record as a time. Moreover, it will still fail when there were already multiple duplicated of the newly inserted record in the database before the insert.
You need to exclude the latest inserted records from the COUNT. But a better idea would probably be to add a UNIQUE constraint for preventing duplicates, so no trigger would be necessary.
If adding a constraint is not possible yet, you should initiate a clean-up process to eliminate the existing duplicates beforehand. Everything else is looks pretty flawed to me, since it is unlikely the current approach will ever bring the table into a state with no duplicates.
You are creating the infinite loop. You just have to remove the insertion part from your trigger.
ELSE
BEGIN
INSERT INTO SDPRawInventory
SELECT * FROM inserted;
END
This should not be in the trigger as trigger is called as part of insertion. you should not write actual insertion in to table in trigger.
Is it possible to have a non-null column where the value is generated at insert by calling a stored procedure the parameters of which are values passed to insert into the row?
For example, I have table User:
| username | name | surname | id |
Insert looks like this:
INSERT INTO USER (username, name, surname)
VALUES ('myusername', 'myname', 'mysurname');
The id column is populated with an (integer) value retrieved by calling stored procedure mystoredproc with parameters myusername, myname, mysurname.
A further question is, would this stored procedure be called on each row, or can it be called in a grouped fashion. For example, I'd like my stored procedure to take the name and append a random integer to it so that that if I insert 100 users with the name 'David', they will get the same id and the stored procedure will be called only once. A bit of a bad example on the second point.
Good day,
Is it possible to have a non-null column where the value is generated at insert by calling a stored procedure
Option 1: please check if this work for you
Specify Default Value for the Column and use "NOT NULL"
create trigger on the table AFTER INSERT
Inside the trigger, you can use the virtual table "inserted" in order to get the inserted values.
Using these values (using the inserted table) you can update the column using the logic you need for all the rows at once
** there is no need to use external SP probably, but you can execute SP from trigger if needed
** All executed by a trigger is in the same transaction as the original query.
would this stored procedure be called on each row
NO! The trigger will be executed once for all rows you insert in the same statement. The inserted table includes all the rows which were inserted. In your update section (step 4) you can update all the rows which were inserted in once and no need to execute something for each row
** If you do use external SP which is executed from the trigger then you can pass it all the inserted table as one using Table-Valued Parameter
------------------- update ---------------
Here is a full example of using this logic:
drop table if exists T;
CREATE TABLE T (id int identity(2,2), c int NOT NULL default 1)
GO
CREATE TRIGGER tr ON T AFTER INSERT
AS BEGIN
SET NOCOUNT ON;
UPDATE T SET T.c = T2.C + 1
FROM inserted T2
INNER JOIN T T1 ON T1.id = T2.id
END
INSERT T(c) values (1) -- I insert the value 1 but the trigger will change it to 1+1=2
select * from T
GO
-- test multiple rows:
INSERT T(c) values (10),(20),(30),(40)
select * from T
GO
DECLARE #rc INT = 0,
#UserID INT = ABS(CHECKSUM(NEWID())) % 1000000 + 1;
WHILE #rc = 0
BEGIN
IF NOT EXISTS (SELECT 1 FROM dbo.Users WHERE UserId= #UserId)
BEGIN
INSERT dbo.Users(UserId) WHERE Username = #UserName SELECT #UserId;
SET #rc = 1;
END
ELSE
BEGIN
SELECT #UserId = ABS(CHECKSUM(NEWID())) % 1000000 + 1,
#rc = 0;
END
END
I have 3 tables tbl_Users, tbl_Protocol and tbl_ProtocolDetails and inside of my trigger on Users, I have to inserted into Protocol and then insert into ProtocolDetails, but I don't know how work the inserted scope.
Something like that:
CREATE TRIGGER tg_Users ON tbl_Users
AFTER INSERT, UPDATE AS
BEGIN
DECLARE #UserId = Int
DECLARE #ProtocolId = Int
DECLARE #UserDetail = NVARCHAR(255)
SELECT
#UserId = user_id,
#UserDetail = user_detail + '#' + user_explanation
FROM INSERTED
INSERT INTO tbl_Protocol (user_id, inserted_date)
VALUES (#UserId, GetDate())
-- Return Inserted Id from tbl_Protocol into #ProtocolDetail then
INSERT INTO tbl_ProtocolDetails (protocol_id, protocol_details)
VALUES (#ProtocolId, #UserDetail)
END
Your trigger has a MAJOR flaw in that you seems to expect to always have just a single row in the Inserted table - that is not the case, since the trigger will be called once per statement (not once for each row), so if you insert 20 rows at once, the trigger is called only once, and the Inserted pseudo table contains 20 rows.
Therefore, code like this:
Select #UserId = user_id,
#UserDetail = user_detail + '#' + user_explanation
From INSERTED;
will fail, since you'll retrieve only one (arbitrary) row from the Inserted table, and you'll ignore all other rows that might be in Inserted.
You need to take that into account when programming your trigger! You have to do this in a proper, set-based fashion - not row-by-agonizing-row stlye!
Try this code:
CREATE TRIGGER tg_Users ON tbl_Users
AFTER INSERT, UPDATE AS
BEGIN
-- declare an internal table variable to hold the inserted "ProtocolId" values
DECLARE #IdTable TABLE (UserId INT, ProtocolId INT);
-- insert into the "tbl_Protocol" table from the "Inserted" pseudo table
-- keep track of the inserted new ID values in the #IdTable
INSERT INTO tbl_Protocol (user_id, inserted_date)
OUTPUT Inserted.user_id, Inserted.ProtocolId INTO #IdTable(UserId, ProtocolId)
SELECT user_id, SYSDATETIME()
FROM Inserted;
-- insert into the "tbl_ProtocolDetails" table from both the #IdTable,
-- as well as the "Inserted" pseudo table, to get all the necessary values
INSERT INTO tbl_ProtocolDetails (protocol_id, protocol_details)
SELECT
t.ProtocolId,
i.user_detail + '#' + i.user_explanation
FROM
#IdTable t
INNER JOIN
Inserted i ON i.user_id = t.UserId
END
There is nothing in this trigger that would handle a multiple insert/update statement. You will need to either use one scenario that will handle multiple records or check how many records were effected with a IF ##ROWCOUNT = 1 else statement. In your example, I would just use something like
insert into tbl_Protocol(user_id, inserted_date)
select user_id, user_detail + '#' + user_explanation
From INSERTED;
As for your detail table, I see Marc corrected his answer to include the multiple lines and has a simple solution or you can create a second trigger on the tbl_Protocol. Another solution I have used in the past is a temp table for processing when I have very complicated triggers.
I have this delete trigger on an SQL database. The record deletes currently and gets written to an audit table. I have been asked to include in this history table a field from another table that is related to the record being deleted based on SurveyID. I thought I could do something like
select #Status = Status from table where Survey = deleted.Survey
But this is incorrect syntax.
ALTER trigger [dbo].[table_Selfdelete]
on [dbo].[table]
after delete
as
Begin
Set nocount on;
Declare #SurveyId int
Declare #StudentUIC varchar(10)
Declare #Status varchar(10)
select #SurveyId = deleted.SurveyID,
#StudentUIC = deleted.StudentUIC
from deleted
select #Status = Status from tbly when SurveyID = deleted.SurveyID
insert into fupSurveyAudit
values(#SurveyId,#StudentUIC,#Status)
End
Arrgh. I think you want this insert in your trigger (and nothing else):
insert into fupSurveyAudit(SurveyId, StudentUIC, status)
select d.SurveyId, d.StudentUIC, y.status
from deleted d left join
tbly y
on d.SurveyId = y.SurveyId;
Notes:
deleted could contain more than one row, so assuming that it has one row can lead to a run-time error or incorrect results.
A left join is needed in case there is no matching row for the status.
You should always include the columns in an insert
Your archive table should have additional columns, such as an identity column and the date of the insert, which are set automatically (and hence not explicitly part of the insert).
Triggers are fired once for each statement (Delete,insert,update) not for each row inside the statement.
You cannot use variables here because when multiple lines are deleted from the table only one line will be inserted in the Audit table because the variable can only hold one value.
You just need a simple insert from the deleted table into the Audit table something like this....
ALTER trigger [dbo].[table_Selfdelete]
on [dbo].[table]
after delete
as
Begin
Set nocount on;
insert into fupSurveyAudit(SurveyId, StudentUIC,[Status])
select d.SurveyID
,d.StudentUIC
,y.[Status]
from deleted d
INNER JOIN tbly y ON y.SurveyID = deleted.SurveyID
End
Try this
ALTER trigger [dbo].[table_Selfdelete]
on [dbo].[table]
after delete
as
Begin
Set nocount on;
insert into fupSurveyAudit -- Better listed the column list here
select
d.SurveyID, d.StudentUIC, y.Status
from
deleted d JOIN tbly y ON d.SurveyID = y.SurveyID
End
all id columns has auto_increment
In my trigger:
ALTER trigger [dbo].[mytrig]
on [dbo].[requests]
after INSERT, UPDATE
as
begin
declare #MyId1 int
set #MyId1 = (select Id from inserted)
declare #MyId2 int
declare #MyId3 int
if (select column1 from inserted) = 1
begin
insert into [dbo].[contracts] select column1,column2,column3 .... from inserted
set #MyId2 = SCOPE_IDENTITY()
insert into [dbo].[History] select column1,column2,column3 .... from inserted
set #MyId3 = SCOPE_IDENTITY()
insert into [dbo].[contracts_depts](Id_Contract ,column5) select #MyId2,column6 from request_depts where Id_request=#MyId1
insert into [dbo].[History_depts] (Id_InHistory,column5) select #MyId3,column6 from request_depts where Id_request=#MyId1
end
end
#MyId1 returns value only after update but not after insert. Do I have to use scope_identity() or something ?
Your main issue is: you're assuming the triggers is called once per row - that is NOT the case!
The trigger is called once per statement, and if your statement affects multiple rows, the Inserted pseudo table will contain multiple rows - so your statement here
set #MyId1 = (select Id from inserted)
really isn't going to work - it will select one arbitrary row (out of however many there are).
You'll need to rewrite your trigger to take this fact into account! Assume that Inserted contains 100 rows - how do you want to deal with that? What are you trying to achieve? Triggers don't return values - they will record into an audit table, or update other rows, or something like that ....