I have the following table: product(id, price, is_deleted)
I want to create a trigger that, when someone deletes a row from the PRODUCT table, instead of deleting it, changes the value of the column 'is_deleted' in that row to '1'.
The row that is to be deleted during the execution of a DELETE task must be temporary in a table called 'deleted'. It must also be the only row that is in the table 'deleted' on that moment.
This is what I thought:
CREATE TRIGGER is_deleted
ON product
FOR INSERT
AS
BEGIN
UPDATE Product, is_deleted = 1
WHERE is_deleted = NULL
END
Is this a good way to do it?
Thanks in advance!
Related
Interbase, Sql, trigger. Can't really understand how to write a trigger of this kind: I have several tables. Each one has a document type, status and an unique number. One table in which i wish to create a trigger is a table that holds a file i post, a status of posting, a doctype corresponding to a table and a unique number linking to a record in the corresponding table. I want to change document status in the corresponding table based on the unique number to a certain status depending on the post result (status) that i change after posting. How can I do it?
Trigger T1 will be executed after update on TABLE1.
Trigger checks if TABLE1.StatusOfPosting changed to some value and depending on result updates TABLE2.DocumentStatus.
Depending on bussienes logic, maybe you will need and BEFORE DELETE trigger.
CREATE TRIGGER T1 FOR TABLE1 AFTER UPDATE POSITION 0
AS
BEGIN
IF (NEW.StatusOfPosting <> OLD.StatusOfPosting and NEW.StatusOfPosting=1) THEN
UPDATE TABLE2
SET TABLE2.DocumentStatus=1
WHERE TABLE2.UniqueNumber = TABLE1.UniqueNumber;
END
I have a simple trigger setup, which is used to insert records into a RentJournal table, whenever there is a record inserted in the UnitAGA table.
The RentJournal table has a primary key ID column named RentJournalID, which is auto incrementing. The UnitAGA table also has a nullable foreign key column named RentJournalID, which links each UnitAGA entry, to its corresponding entry in RentJournal table (which is inserted through the Trigger below).
Problem is that currently this Trigger is only inserting values into RentJournal table. But now I want to also fetch the ID assigned for each RentJournal entry through this Trigger, and write that into the corresponding UnitAGA record, whose insert actually triggered the Trigger in the first place. How do I do this ?
The Trigger code as of right now is this:
USE [RentDB]
GO
ALTER TRIGGER [RTS].[InsertRentJournalEntry]
ON [RTS].[UnitAGA]
AFTER INSERT
AS
BEGIN
INSERT INTO RTS.RentJournal
(UnitId, AdjustmentType, EffectiveDate, ReferenceFormNo)
SELECT
UnitId, 'AGA', EffectiveDate, ReferenceFormNo FROM inserted
END
Have a look at the INSERT logical table that is available in insert triggers:
DML triggers use the deleted and inserted logical (conceptual) tables. They are structurally similar to the table on which the trigger is defined, that is, the table on which the user action is tried. The deleted and inserted tables hold the old values or new values of the rows that may be changed by the user action. For example, to retrieve all values in the deleted table, use: SELECT * FROM deleted
http://technet.microsoft.com/en-us/library/ms189799.aspx
Then use ##IDENTITY to get the value of the identity column on your RentJournal table.
So you should be able to do something like:
update INSERTED set RentJournalID = ##IDENTITY
I have 6 tables:
Staff ( StaffID, Name )
Product ( ProductID, Name )
Faq ( FaqID, Question, Answer, ProductID* )
Customer (CustomerID, Name, Email)
Ticket ( TicketID, Problem, Status, Priority, LoggedTime, CustomerID* , ProductID* )
TicketUpdate ( TicketUpdateID, Message, UpdateTime, TicketID* , StaffID* )
Question to be answered:
Given a Product ID, remove the record for that Product. When a product is removed all associated FAQ can stay in the database but should have a null reference in the ProductID field. The deletion of a product should, however, also remove any associated tickets and their updates. For completeness deleted tickets and their updates should be copied to an audit table or a set of tables that maintain historical data on products, their tickets and updates. (Hint: you will need to define a additional table or set or tables to maintain this audit information and automatically copy any deleted tickets and ticket updates when a product is deleted). Your audit table/s should record the user which requested the deletion and the timestamp for the deletion operation.
I have created additional maintain_audit table:
CREATE TABLE maintain_audit(
TicketID INTEGER NOT NULL,
TicketUpdateID INTEGER NOT NULL,
Message VARCHAR(1000),
mdate TIMESTAMP NOT NULL,
muser VARCHAR(128),
PRIMARY KEY (TicketID, TicketUpdateID)
);
Addittionally I have created 1 function and trigger:
CREATE OR REPLACE FUNCTION maintain_audit()
RETURNS TRIGGER AS $BODY$
BEGIN
INSERT INTO maintain_audit (TicketID,TicketUpdateID,Message,muser,mdate)
(SELECT Ticket.ID,TicketUpdate.ID,Message,user,now() FROM Ticket, TicketUpdate WHERE Ticket.ID=TicketUpdate.TicketID AND Ticket.ProductID = OLD.ID);
RETURN OLD;
END;
$BODY$
LANGUAGE plpgsql;
CREATE TRIGGER maintain_audit
BEFORE DELETE
ON Product
FOR EACH ROW
EXECUTE PROCEDURE maintain_audit()
DELETE FROM Product WHERE Product.ID=30;
When I run this all I get this :
ERROR: null value in column "productid" violates not-null constraint
CONTEXT: SQL statement "UPDATE ONLY "public"."faq" SET "productid" = NULL WHERE $1 OPERATOR(pg_catalog.=) "productid""
GUYS,Could you help me in sorting out this problem?
What you probably want is triggers. Not sure what RDBMS you are using, but that's where you should start. I started from zero and had triggers up and running in a somewhat similar situation within an hour.
In case you don't already know, triggers do something after a specific type of query happens on a table, such as an insert, update or delete. You can do any type of query.
Another tip I would give you is not to delete anything, since that could break data integrity. You could just add an "active" boolean field, set active to false, then filter those out in most of your system's queries. Alternatively, you could just move the associated records out to a Products_archive table that has the same structure. Easy to do with:
select * into destination from source where 1=0
Still, I would do the work you need done using triggers because they're so automatic.
create a foreign key for Ticket.product_id, and TicketUpdate.Ticket_id which has ON DELETE CASCADE. This will automatically delete all tickets and ticketupdates when you delete the product.
create an audit table for Product deleters with product_id, user and timestamp. audit tables for ticket,ticketUpdate should mirror them exactly.
create a BEFORE DELETE TRIGGER for table Ticket which copies tickets to the audit table.
Do the same for TicketUpdate
Create an AFTER DETETE Trigger on Products to capture who requested a product be deleted in the product audit table.
In table FAQ create Product_id as a foreign key with ON DELETE SET NULL
i have what seems like a basic scenario for a db trigger in SQL server and i am running into an issue.
i have table Users (id, name, phone, etc) and i have tables UsersHistory (id, user_id action, fields, timestamp)
i want a database trigger where anytime inserts, updates or deletes into Users, i want a new record created in UsersHistory with the user id and the action that was done (insert new, updated fields, deleted id. Basically an audit log table.
this is how far i got, but i can't figure out how to:
Get the id on modify and deletes and also
How to get a list of fields that have changed and the action that was committed (insert, delete, update)
CREATE TRIGGER Update_Users_History
ON Users
AFTER INSERT,DELETE,UPDATE
AS
BEGIN
-- Insert statements for trigger here
insert into UsersHistory (user_id, [action], [fields], timestamp)
select max(id) as user_id, {action ??},{fields??} getdate() from Users)
END
GO
any suggestions?
The easiest might be to just simply create three triggers - one for each operation:
CREATE TRIGGER trgUserInsert
ON dbo.User AFTER INSERT
AS BEGIN
INSERT INTO dbo.UserHistory............
END
CREATE TRIGGER trgUserDelete
ON dbo.User AFTER DELETE
AS BEGIN
INSERT INTO dbo.UserHistory............
END
CREATE TRIGGER trgUserUpdate
ON dbo.User AFTER UPDATE
AS BEGIN
INSERT INTO dbo.UserHistory............
END
That way, things are simple and you easily understand what you're doing, plus it gives you the ability to turn off a trigger for a single operation, if you e.g. need to insert or delete a huge list of items.
Inside the trigger, you have two "pseudo-tables" - Inserted (for INSERT and UPDATE) and Deleted (for UPDATE and DELETE). These pseudo tables contain the values for the newly inserted values (or the updated ones in UPDATE), or the ones that were deleted (for DELETE) or have been updated (the old values, before the update, for the UPDATE operation).
You need to be aware that a trigger will be called once even if you update a huge number of rows, e.g. Inserted and Deleted will typically contain multiple rows.
As a sample, you could write a "AFTER INSERT" trigger like this (just guessing what your table structure might be....):
CREATE TRIGGER trgUserInsert
ON dbo.User AFTER INSERT
AS BEGIN
INSERT INTO
dbo.UserHistory(UserID, Action, DateTimeStamp, AuditMessage)
SELECT
i.UserID, 'INSERT', getdate(), 'User inserted into table'
FROM
Inserted i
END
You are looking for a way to find out which "action" this trigger caused? I don't see any way to do this - another reason to keep the three trigger separate. The only way to find this out would be to count the rows in the Inserted and Updated tables:
if both counts are larger than zero, it's an UPDATE
if the Inserted table has rows, but the Deleted does not, it's an INSERT
if the Inserted table has no rows, but the Deleted does, it's a DELETE
You're also looking for a "list of fields that were updated" - again, you won't have any simple solution, really. You could either just loop through the fields in the "Users" table that are of interest, and check
IF UPDATE(fieldname) ......
but that gets a bit tedious.
Or you could use the COLUMNS_UPDATED() function - this however doesn't give you a nice list of column names, but a VARBINARY in which each column is basically one bit, and if it's turned on, that column was updated. Not very easy to use.....
If you really want to create a single, big trigger, this could serve as a basis - it detects what operation has caused the trigger to fire, and will insert entries into your User_History table:
CREATE TRIGGER trgUser_Universal
ON dbo.Users
AFTER INSERT, UPDATE, DELETE
AS BEGIN
DECLARE #InsHasRows BIT = 0
DECLARE #DelHasRows BIT = 0
IF EXISTS(SELECT TOP 1 * FROM INSERTED)
SET #InsHasRows = 1
IF EXISTS(SELECT TOP 1 * FROM DELETED)
SET #DelHasRows = 1
DECLARE #TriggerAction VARCHAR(20)
IF #InsHasRows = 1 AND #DelHasRows = 1
SET #TriggerAction = 'UPDATE'
ELSE
IF #InsHasRows = 1
SET #TriggerAction = 'INSERT'
ELSE
SET #TriggerAction = 'DELETE'
IF #InsHasRows = 1
INSERT INTO dbo.UsersHistory(user_id, [action], [fields], timestamp)
SELECT i.UserId, #TriggerAction, null, getdate()
FROM INSERTED i
ELSE
INSERT INTO dbo.UsersHistory(user_id, [action], [fields], timestamp)
SELECT d.UserId, #TriggerAction, null, getdate()
FROM DELETED d
END
I haven't included the figuring out which fields have been updated part just yet - that's left as an exercise to the reader :-)
Does that help at all?
There are two "tables" that are used in the trigger. One is DELETED and one is INSERTED. When you delete a row, that row is captured in the DELETED table. When you insert a row, that row is captured in the INSERTED table. When you update a row, the old row is in the DELETED table, and the new row is in the INSERTED table. The DELETED and INSERTED tables have the same schema as the table on which you are adding the trigger.
You might check out this solution that will create a query for you that will make all the auditing triggers you want, as well as the table in which to store the audits, excluding any selected tables. It will only do UPDATE triggers, but could easily be modified to make INSERT and DELETE triggers as well.
I wish to make a trigger but i'm not sure how to grab the data for whatever caused the trigger.
I have a simlpe table.
FooId INT PK NOT NULL IDENTITY
Name VARCHAR(100) NOT NULL
I wish to have a trigger so that when an UPDATE, INSERT or DELETE occurs, i then do the following.
Pseduocode
IF INSERT
Print 'Insert' & Name
ELSE IF UPDATE
Print 'Update' & FooId & Name
ELSE IF DELETE
Print 'Delete' & FooId & Name
Now, I know how to make a trigger for a table.
What i don't know how to do is figure out the values based on what the trigger type is.
Can anyone help?
Edit: Not sure if it helps, but db is Sql Server 2008
the pseudo table "inserted" contains the new data, and "deleted" table contains the old data.
You can do something like
create trigger mytrigger on mytable for insert, update, delete
as
if ( select count(*) from inserted ) > 0
-- insert or update
select FooId, Name from inserted
else
-- delete
select FooId, Name from deleted
To clarify all the comments made by others, on an insert, the inserted table contains data and deleted is empty. On a delete, the situation is reversed. On an update, deleted and inserted contain the "before" and "after" copy of any updated rows.
When you are writing a trigger, you have to account for the fact that your trigger may be called by a statement that effects more than one row at a time.
As others have pointed out, you reference the inserted table to get the values of new values of updated or inserted rows, and you reference the deleted table to get the value of deleted rows.
SQL triggers provide an implicitly-defined table called "inserted" which returns the affected rows, allowing you to do things like
UPDATE mytable SET mytimestamp = GETDATE() WHERE id IN (SELECT id FROM inserted)
Regarding your code sample, you'll want to create separate INSERT, UPDATE and DELETE triggers if you are performing separate actions for each.
(At least, this is the case in SQL Server... you didn't specify a platform.)
On 2008, there is also MERGE command. How do you want to handle it?
Starting from 2008, there are four commands you can modify a table with:
INSERT, UPDATE, DELETE, and MERGE:
http://blogs.conchango.com/davidportas/archive/2007/11/14/SQL-Server-2008-MERGE.aspx
http://sqlblogcasts.com/blogs/grumpyolddba/archive/2009/03/11/reasons-to-move-to-sql-2008-merge.aspx
What do you want your trigger to do when someone issues a MERGE command against your table?