How to do a log using a trigger on update?

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Hey guys, I'm really bad/new at T-SQL but I need it for a project I'm working on.

What I want to do here is to be able to populate a table (logs) with date from another table (events) when this is updated (essentially making a log).

I have this pseudocode:

SQL

CREATE TRIGGER [dbo].[EventUpdate]
   ON  [dbo].[Events]
   AFTER UPDATE
AS
BEGIN
    SET NOCOUNT ON;

    WHILE tablesupdated.hasNext()
    BEGIN
        [dbo].[Logs].[date] = dateTime.Now();
        [dbo].[Logs].[user] = "John";
        [dbo].[Logs].[changes] = [dbo].[Events].[updatedTable].previousval() + "-->" + [dbo].[Events].[updatedTable].afterval();
        [dbo].[Logs].[eventId] = [dbo].[Events].[id];
    END
END
GO

It's more to give you an idea of what I want and how bad I am at this... can you guys help please?

PS: I'm completely open to new suggestion on how to get this done.

Posted 9-Mar-15 23:56pm

varmartins

Updated 9-Mar-15 23:58pm

v2

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Comments

Kornfeld Eliyahu Peter 10-Mar-15 6:02am

Are you want to keep a data history upon update?

varmartins 10-Mar-15 6:03am

I didn't understand the question sorry. But what I want is for whenever a value(s) is updated on the table Events the changes are recorded on Logs

John C Rayan 10-Mar-15 6:15am

Hi look at the solution 2 which is what you need. replace the columnname with your column or columnlist.

2 solutions

Solution 1

Within a trigger there are a pair of conceptual tables called "inserted" and "deleted" which contains the records that are being updated (new and previous data). (See CREATE TRIGGER[^] documentation - it has an audit example included).

You need to iterate through the rows in this pair of tables and log them to the table.

Posted 10-Mar-15 0:06am

Duncan Edwards Jones

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John C Rayan · Accepted Answer · 2015-03-10T00:11:00

Solution 2

SQL

CREATE TRIGGER [dbo].[EventUpdate]
   ON  [dbo].[Events]
   AFTER UPDATE
AS
BEGIN
       SET NOCOUNT ON;

       INSERT INTO [dbo].Logs([date],[user],[changes],[eventId])
             SELECT getdate(), 'john', I.columnname + '-->' + D.columnname, I.id
             FROM Inserted I
                  INNER JOIN Deleted D ON I.id = D.id

END
GO

Posted 10-Mar-15 0:11am

John C Rayan

Comments

varmartins 10-Mar-15 6:27am

Thanks mate ;)