Inserted, Deleted Logical table in SQL Server

There are Inserted and Deleted logical tables in SQL Server. These tables are automatically created and managed by SQL Server internally to hold recently inserted, deleted and updated values during DML operations (Insert,Update,Delete) on a database table.

Use of logical tables

Basically, logical tables are used by triggers for the following purpose:

1. To test data manipulation errors and take suitable actions based on the errors.
2. To find the difference between the state of a table before and after the data modification and take actions based on that difference.

Inserted logical Table

The Inserted table holds the recently inserted or updated values means new data values. Hence newly added and updated records are inserted into the Inserted table.

Suppose we have Employee table as shown in fig. Now We need to create two triggers to see data with in logical tables Inserted and Deleted.

CREATE TRIGGER trg_Emp_Ins
ON Employee
FOR INSERT
AS 

begin 

SELECT * FROM INSERTED -- show data in Inserted logical table
SELECT * FROM DELETED -- show data in Deleted logical table 

end

 

Now insert a new record in Employee table to see data with in Inserted logical table.

INSERT INTO Employee(EmpID, Name, Salary) VALUES(3,'Avin',23000) 

SELECT * FROM Employee

 

Deleted logical Table

The Deleted table holds the recently deleted or updated values means old data values. Hence old updated and deleted records are inserted into the Deleted table.

CREATE TRIGGER trg_Emp_Upd
ON Employee
FOR UPDATE
AS 

begin
SELECT * FROM INSERTED -- show data in INSERTED logical table
SELECT * FROM DELETED -- show data in DELETED logical table
end

 

--Now update the record in Employee table to see data with in Inserted and Deleted logical tables 

Update Employee set Salary=43000 where EmpID=3

 
SELECT * FROM Employee

 

We could not create the logical tables or modify the data with in the logical tables. Except triggers, When you use the OUTPUT clause in your query, logical tables are automatically created and managed by SQL Server. OUTPUT clause also has access to Inserted and Deleted logical tables just like triggers.

http://www.dotnet-tricks.com/Tutorial/sqlserver/7OT8250912-Inserted,-Deleted-Logical-table-in-SQL-Server.html