Passing new / old parameters in audit tables?

Question

So as I understand, the audit tables are some kind of tracking tables (ie to capture changes in base table)

How INSERT / UPDATE op works with old and new values? Dunno how to code it

I need to write old and new values of AddressLine1 FROM Person.Address

That's all what I have:

USE AdventureWorks2012;
GO

    -- AL1 is AddressLine1
-- also what about primary key???
CREATE TABLE AuditTable
(
    AL1Old      nvarchar(60)    not null,
    AL1New      nvarchar(60)    not null,
);
GO

-- should I update AuditTable there? 
-- I don't know how to insert Old and New value by trigger...
CREATE TRIGGER triggy
ON Person.Address
AFTER INSERT, UPDATE 
AS
-- ???
GO

Answer 1

If you want to insert the old and new data in a trigger, then that'll only work in an UPDATE trigger - the INSERT trigger doesn't have any "old" data, obviously.

Basically, you need to get the old data from the Deleted pseudo table, and the new data from the Inserted pseudo table.

Also: be aware that a trigger is called once per statement and both pseudo tables can (and will!) contain multiple rows -so program your trigger accordingly.

To handle the Addressline1 column - try something like this (and yes, I would also recommend to include the primary key to identify what row this data is for!)

-- AL1 is AddressLine1
-- also what about primary key???
CREATE TABLE AuditTable
(
    PrimaryKey INT NOT NULL,
    AL1Old      nvarchar(60)    not null,
    AL1New      nvarchar(60)    not null,
);
GO

-- I don't know how to insert Old and New value by trigger...
CREATE TRIGGER addressUpdateTrigger
ON Person.Address
AFTER UPDATE 
AS
    INSERT INTO dbo.AuditTable(PrimaryKey, AL1Old, AL1New)
       SELECT
          Inserted.AddressID,      -- primary key
          Deleted.AddressLine1,    -- old data
          Inserted.AddressLine1    -- new data
       FROM 
          Inserted
       INNER JOIN
          Deleted on Inserted.AddressID = Deleted.AddressID

GO