I have a simple details table like so:
listid
custid
status
last_changed
The primary key consists of both listid and custid.
Now I'm trying to setup a trigger that sets the last_changed column to the current datetime every time an insert or update happens. I've found lots of info on how to do that with a single PK column, but with multiple PKs it gets confusing on how to correctly specify the PKs from the INSERTED table.
The trigger has to work in SQL Server 2005/2008/R2.
Thanks for a working trigger code!
Bonus would be to also check if the data was actually altered and only update last_changed in that case but for the sake of actually understanding how to correctly code the main question I'd like to see this as a separate code block if at all.
Hmm.... just because the primary key is made up of two columns shouldn't really make a big difference....
CREATE TRIGGER dbo.trgAfterUpdate ON dbo.YourTable
AFTER INSERT, UPDATE
AS
UPDATE dbo.YourTable
SET last_changed = GETDATE()
FROM Inserted i
WHERE dbo.YourTable.listid = i.listid AND dbo.YourTable.custid = i.custid
You just need to establish the JOIN between the two tables (your own data table and the Inserted pseudo table) on both columns...
Are am I missing something?? .....
CREATE TRIGGER dbo.trgAfterUpdate ON dbo.YourTable
AFTER INSERT, UPDATE
AS
UPDATE dbo.YourTable
SET last_changed = GETDATE()
FROM Inserted i
JOIN dbo.YourTable.listid = i.listid AND dbo.YourTable.custid = i.custid
WHERE NOT EXISTS
(SELECT 1 FROM Deleted D Where D.listid=I.listid AND D.custid=i.custid AND (D.status=i.status)
Here i assuming that stasus column is not nullable. If yes, you should add additional code to check if one of columns is NULL
You can check every field in trigger by comparing data from inserted and deleted table like below :
CREATE TRIGGER [dbo].[tr_test] ON [dbo].[table]
AFTER INSERT, UPDATE
AS
BEGIN
DECLARE #old_listid INT
DECLARE #old_custid INT
DECLARE #old_status INT
DECLARE #new_listid INT
DECLARE #new_custid INT
DECLARE #new_status INT
SELECT #old_listid=[listid], #old_custid=[custid], #old_status = [status] FROM [deleted]
SELECT #new_listid=[listid], #new_custid=[custid], #new_status = [status] FROM [inserted]
IF #oldstatus <> #new_status
BEGIN
UPDATE TABLE table SET last_changed = GETDATE() WHERE [listid] = #new_listid AND [custid] = #new_custid
END
END
Related
I need to create a new DATETIME column in SQL Server that will always contain the date of when the record was created, and then it needs to automatically update whenever the record is modified. I've heard people say I need a trigger, which is fine, but I don't know how to write it. Could somebody help with the syntax for a trigger to accomplish this?
In MySQL terms, it should do exactly the same as this MySQL statement:
ADD `modstamp` timestamp NULL
DEFAULT CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP
Here are a few requirements:
I can't alter my UPDATE statements to set the field when the row is modified, because I don't control the application logic that writes to the records.
Ideally, I would not need to know the names of any other columns in the table (such as the primary key)
It should be short and efficient, because it will happen very often.
SQL Server doesn't have a way to define a default value for UPDATE.
So you need to add a column with default value for inserting:
ADD modstamp DATETIME2 NULL DEFAULT GETDATE()
And add a trigger on that table:
CREATE TRIGGER tgr_modstamp
ON **TABLENAME**
AFTER UPDATE AS
UPDATE **TABLENAME**
SET ModStamp = GETDATE()
WHERE **ID** IN (SELECT DISTINCT **ID** FROM Inserted)
And yes, you need to specify a identity column for each trigger.
CAUTION: take care when inserting columns on tables where you don't know the code of the application. If your app have INSERT VALUES command without column definition, it will raise errors even with default value on new columns.
This is possible since SQL Server 2016 by using PERIOD FOR SYSTEM_TIME.
This is something that was introduced for temporal tables but you don't have to use temporal tables to use this.
An example is below
CREATE TABLE dbo.YourTable
(
FooId INT PRIMARY KEY CLUSTERED,
FooName VARCHAR(50) NOT NULL,
modstamp DATETIME2 GENERATED ALWAYS AS ROW START NOT NULL,
MaxDateTime2 DATETIME2 GENERATED ALWAYS AS ROW END HIDDEN NOT NULL,
PERIOD FOR SYSTEM_TIME (modstamp,MaxDateTime2)
)
INSERT INTO dbo.YourTable (FooId, FooName)
VALUES (1,'abc');
SELECT *
FROM dbo.YourTable;
WAITFOR DELAY '00:00:05'
UPDATE dbo.YourTable
SET FooName = 'xyz'
WHERE FooId = 1;
SELECT *
FROM dbo.YourTable;
DROP TABLE dbo.YourTable;
It has some limitations.
The time stored will be updated by the system and always be UTC.
There is a need to declare a second column (MaxDateTime2 above) that is completely superfluous for this use case. But it can be marked as hidden making it easier to ignore.
Okay, I always like to keep track of not only when something happened but who did it!
Lets create a test table in [tempdb] named [dwarfs]. At a prior job, a financial institution, we keep track of inserted (create) date and updated (modify) date.
-- just playing
use tempdb;
go
-- drop table
if object_id('dwarfs') > 0
drop table dwarfs
go
-- create table
create table dwarfs
(
asigned_id int identity(1,1),
full_name varchar(16),
ins_date datetime,
ins_name sysname,
upd_date datetime,
upd_name sysname,
);
go
-- insert/update dates
alter table dwarfs
add constraint [df_ins_date] default (getdate()) for ins_date;
alter table dwarfs
add constraint [df_upd_date] default (getdate()) for upd_date;
-- insert/update names
alter table dwarfs
add constraint [df_ins_name] default (coalesce(suser_sname(),'?')) for ins_name;
alter table dwarfs
add constraint [df_upd_name] default (coalesce(suser_sname(),'?')) for upd_name;
go
For updates, but the inserted and deleted tables exist. I choose to join on the inserted for the update.
-- create the update trigger
create trigger trg_changed_info on dbo.dwarfs
for update
as
begin
-- nothing to do?
if (##rowcount = 0)
return;
update d
set
upd_date = getdate(),
upd_name = (coalesce(suser_sname(),'?'))
from
dwarfs d join inserted i
on
d.asigned_id = i.asigned_id;
end
go
Last but not least, lets test the code. Anyone can type a untested TSQL statement in. However, I always stress testing to my team!
-- remove data
truncate table dwarfs;
go
-- add data
insert into dwarfs (full_name) values
('bilbo baggins'),
('gandalf the grey');
go
-- show the data
select * from dwarfs;
-- update data
update dwarfs
set full_name = 'gandalf'
where asigned_id = 2;
-- show the data
select * from dwarfs;
The output. I only waited 10 seconds between the insert and the delete. Nice thing is that who and when are both captured.
Create trigger tr_somename
On table_name
For update
As
Begin
Set nocount on;
Update t
Set t.field_name = getdate()
From table_name t inner join inserted I
On t.pk_column = I.pk_column
End
ALTER TRIGGER [trg_table_name_Modified]
ON [table_name]
AFTER UPDATE
AS
Begin
UPDATE table_name
SET modified_dt_tm = GETDATE() -- or use SYSDATETIME() for 2008 and newer
FROM Inserted i
WHERE i.ID = table_name.id
end
I need to insert records into a production table. The problem is that one of the fields needs to be the same value as the primary key.
In the example below, the Insert query is dropping '99' into [AlsoMyID]. But that's just a placeholder. It needs to be whatever value is going into [MyID].
How do I write the Insert query so that the system will add the same PK value to both [MyID] and [AlsoMyID]?
Drop table #mylittletable
Create table #Mylittletable (
[MyID] int IDENTITY(1,1) NOT FOR REPLICATION NOT NULL,
[AlsoMyID] int,
[ActualData] varchar(1))
Select * from #Mylittletable
Insert into #Mylittletable values (99,'x')
Select * from #Mylittletable
If you're interested in the background, the developer is using AlsoMyID as a linking field so any number of records can be linked together using the original primary key value. That said, I have no control over the table structure.
Firstly, you cannot specify the value for identity column unless you use set identity_insert on. so according to your requirement, you need to insert the same value to AlsoMyID as MyID.
You can work it out as flowing:
insert into Mylittletable
select ##IDENTITY+1,'1'
With this trigger on the table you can insert anything on the alsoMyID-column and that will be overwritten with what get's set in the myID-column.
create trigger tr_Mylittletable ON Mylittletable
AFTER INSERT AS
BEGIN
declare #ID int = (select MyID from inserted)
update Mylittletable set AlsoMyID = #ID where MyID = #ID
END
NOTE: This only works when making inserts of one line at a time!
In my SQl Server I have a table of around 40 attributes/columns. There is a daily load which might update any of these columns. I want to capture the changes in these columns in a separate table with a reason code column telling which column value changed. There might be instances where more than one column value might get changed in a single daily load, in that case the changed log table should capture all these changes separately in rows with each row depicting the individual change.
For Example:
TableA(column1(pk),column2,column3,column4)
values(1,100,ABC,999)
After update:
TableA(column1(pk),column2,column3,column4)
values(1,100,ACD,901)
The corresponding change log table should have two entries:
TabChangeLog(column1,before,after,reason);
values(1,ABC,ACD,'column3 changed')
values(1,999,901,'column4 changed')
I tried implementing this through triggers but am not able to figure out a way to separate each of these changes in separate rows when there are more than one changes. Please help
You need to create a trigger like :
create trigger trigger_name
instead of update as
if update(column1)
begin
insert into TabChangeLog
select inserted.column1, inserted.column3, deleted.column3, 'column3', 'update/change'
from inserted i inner join deleted d
on i.column1 = d.column2
end
if update(column2)
begin
insert into TabChangeLog
select inserted.column1, inserted.column2, deleted.column2, 'column2', 'update/change'
from inserted i inner join deleted d
on i.column1 = d.column2
end
...
https://www.tutorialgateway.org/instead-of-update-triggers-in-sql-server/
Microsoft SQL Server 2016 has a thing called Temporal Tables which would probably simplify your job a lot. It lets you rewind a dataset through time to see the changes:
https://learn.microsoft.com/en-us/sql/relational-databases/tables/temporal-tables?view=sql-server-2017
If you don't want to go that route and use triggers instead. UPDATE triggers have two tables inserted and deleted that let you know what the row state was before and after.
*Edit: These are tables so you have to use SELECT INTO etc to interact with them you can't do conditional logic (if /else)
CREATE TABLE [dbo].[Table1](
[Id] [int] NOT NULL,
[Tail] [int] NOT NULL,
CONSTRAINT [PK_Table1_1] PRIMARY KEY CLUSTERED
(
[Id] ASC
)
)
CREATE TABLE Table1_Audit
(
Audit varchar(100)
)
--drop trigger Table1_OnUPDATE
CREATE TRIGGER Table1_OnUPDATE
ON dbo.Table1
AFTER UPDATE
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
-- Insert statements for trigger here
INSERT INTO Table1_Audit ([Audit])
select CONCAT('Tail changed to' ,inserted.Tail,' for pk Id=',inserted.Id) from inserted inner join
deleted on inserted.Id = deleted.Id --pk must be the same
where
inserted.Tail <> deleted.Tail --field x must be different
END
GO
--truncate table Table1_Audit
--update Table1 set Tail = 5
select * from Table1_Audit
I'm making a simple table with names, emails etc, but I also have a ModifiedDate. My idea is to use a trigger after both insert and update, and insert the current date. Thus if anyone does anything (except delete) to that column, the date should reflect that.
This is however not working.
CREATE TRIGGER ModDate
ON X
AFTER INSERT, UPDATE
AS
BEGIN
INSERT INTO X (ModifiedDate)
VALUES (GETDATE())
END
Now I have a couple of values that can't be null, and what this seems to do is try and create a new row. I would like it to insert the date into the row that is currently being acted upon, I have no idea how though. Also what if I add 5 rows at once ?
You need to join the inserted virtual table in the trigger to limit the rows that get updated to those actually changed. Try this:
CREATE TRIGGER ModDate
ON TableX
AFTER INSERT, UPDATE
AS
BEGIN
UPDATE X
SET ModifiedDate = GETDATE()
FROM TableX X
JOIN inserted i ON X.key = i.key -- change to whatever key identifies
-- the tuples
END
Like #ZoharPeled correctly pointed out in a comment below there's really not much point in having the trigger update the date on insert - it would be better to use getdate() as the default value on the column (or even as another column InsertedDate if you want to track when records were initially created) and have the trigger only modify the ModifiedDate column after updates.
See the documentation for more information on the inserted and deleted tables.
CREATE TRIGGER ModDate
ON TableX
FOR INSERT, UPDATE
AS
BEGIN
UPDATE TableX
SET ModifiedDate = GETDATE()
WHERE Id = (Select Id from Inserted)
END
If you don't have keys on the insert data and you are not in command of the sql to add a default on the modifieddate column, you can get the insert trigger where the modifieddate column is null:
CREATE TRIGGER ModDate
ON TableX
AFTER INSERT
AS
BEGIN
UPDATE tableX SET ModifiedDate = GETDATE() where modifieddate is null
END
I have a table that has a composite primary key made from 3 columns, let's say A, B, C. I want to create a trigger that on UPDATE will check that these three columns won't be changed. This is what I have so far, but it doesn't seem to work:
CREATE TRIGGER TableTrigger
ON Table
AFTER INSERT, UPDATE AS
BEGIN
IF (EXISTS (SELECT * FROM inserted) AND EXISTS (SELECT * FROM deleted))
BEGIN
-- Update Operation
IF (SELECT COUNT(*) FROM inserted WHERE A IS NOT NULL OR B IS NOT NULL OR C IS NOT NULL) > 0
BEGIN
RAISERROR('Error, you cannot change Primary Key columns', 16, 1)
ROLLBACK
RETURN
END
END
I was expecting that if I update some values in a table, in inserted the values for the columns I don't update to be NULL, but it's not like that. I read somewhere that I need to look both in inserted and deleted to see if these values changed. So my question is this, can I check this without using a cursor?
Thank you.
You could do
CREATE TRIGGER TableTrigger
ON Table
AFTER UPDATE AS
BEGIN
IF UPDATE(A) OR UPDATE(B) OR UPDATE(C)
BEGIN
RAISERROR('Error, you cannot change Primary Key columns', 16, 1)
ROLLBACK
RETURN
END
END
Or deny update permissions on those columns.
Both approaches would deny any attempt to update the PK columns irrespective of whether or not the values actually change. SQL Server does not have row level triggers and unless there is an IDENTITY column in the table (guaranteed immutable) there is no reliable way to tell in a trigger if the PK was actually updated.
For example the INSERTED and DELETED tables in an UPDATE trigger on the table below would be identical for both the UPDATE statements.
CREATE TABLE T(C INT PRIMARY KEY);
INSERT INTO T VALUES (1),(-1)
/*Both values swapped*/
UPDATE T SET C = -C
/*Both values left the same*/
UPDATE T SET C = C