SQL Server Update Trigger, Get fields before and after updated

SQL Server triggers have access to 2 "magic" tables that contain a row for each row that was inserted, updated, or deleted in the statement that caused the trigger to execute.

To find all of the inserted rows on a INSERT statement:

select * from inserted

For all of the deleted rows on a DELETE statement:

select * from deleted

For UPDATE statements, each row updated will be present in both the inserted and deleted tables. The inserted table will hold the new value of the row after the update statement, and the deleted table will hold the old value of the row just before the update statement. Join between the two tables to get what you need:

select i.*, d.*
from inserted i
join deleted d on (i.id = d.id)

you'll want the special trigger deleted and inserted tables. From MSDN:

In DML triggers, the inserted and deleted tables are primarily used to perform the following: Extend referential integrity between tables. Insert or update data in base tables underlying a view. Test for errors and take action based on the error. Find the difference between the state of a table before and after a data modification and take actions based on that difference. The deleted table stores copies of the affected rows during DELETE and UPDATE statements. During the execution of a DELETE or UPDATE statement, rows are deleted from the trigger table and transferred to the deleted table. The deleted table and the trigger table ordinarily have no rows in common. The inserted table stores copies of the affected rows during INSERT and UPDATE statements. During an insert or update transaction, new rows are added to both the inserted table and the trigger table. The rows in the inserted table are copies of the new rows in the trigger table.

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