Dear Jitendra Kumar,
Why to use identity in SQL server?
Very often we would like the value of the primary key field to be created automatically every time a new record is inserted. We would like to create an auto-increment field in a table. For this you will use identity in SQL.
How to write query?
Use the IDENTITY property with CREATE TABLE
This example creates a new table using the IDENTITY property for an automatically incrementing identification number.
IF EXISTS(SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_NAME = 'new_employees')
DROP TABLE new_employees
CREATE TABLE new_employees
id_num int IDENTITY (1,1),
fname varchar (20),
(fname, minit, lname)
('Karin', 'F', 'Josephs')
(fname, minit, lname)
('Pirkko', 'O', 'Koskitalo')
It returns the last IDENTITY value produced on a connection, regardless of the table that produced the value, and regardless of the scope of the statement that produced the value.
@@IDENTITY will return the last identity value entered into a table in your current session. While @@IDENTITY is limited to the current session, it is not limited to the current scope. If you have a trigger on a table that causes an identity to be created in another table, you will get the identity that was created last, even if it was the trigger that created it.
It returns the last IDENTITY value produced on a connection and by a statement in the same scope, regardless of the table that produced the value.
SCOPE_IDENTITY(), like @@IDENTITY, will return the last identity value created in the current session, but it will also limit it to your current scope as well. In other words, it will return the last identity value that you explicitly created, rather than any identity that was created by a trigger or a user defined function.
It returns the last IDENTITY value produced in a table, regardless of the connection that created the value, and regardless of the scope of the statement that produced the value.
IDENT_CURRENT is not limited by scope and session; it is limited to a specified table. IDENT_CURRENT returns the identity value generated for a specific table in any session and any scope.
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