Difference between @@IDENTITY, SCOPE_IDENTITY, IDENT_CURRENT

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Introduction

In most of our application scenario, we need to get latest inserted row information through SQL query. And for that, we have multiple options like:

@@IDENTITY
SCOPE_IDENTITY
IDENT_CURRENT

All three functions return last-generated identity values. However, the scope and session on which last is defined in each of these functions differ.

Compare

@@IDENTITY

It returns the last identity value generated for any table in the current session, across all scopes.

Let me explain this... suppose we create an insert trigger on table which inserts a row in another table with generate an identity column, then @@IDENTITY returns that identity record which is created by trigger.

SCOPE_IDENTITY

It returns the last identity value generated for any table in the current session and the current scope.

Let me explain this... suppose we create an insert trigger on table which inserts a row in another table with generate an identity column, then SCOPE_IDENTITY result is not affected but if a trigger or a user defined function is affected on the same table that produced the value returns that identity record then SCOPE_IDENTITY returns that identity record which is created by trigger or a user defined function.

IDENT_CURRENT

It returns the last identity value generated for a specific table in any session and any scope.

In other words, we can say it is not affected by scope and session, it only depends on a particular table and returns that table related identity value which is generated in any session or scope.

SQL Query

I am explaining the above process with the help of some sample query, hope it helps:

CREATE TABLE Parent(id int IDENTITY);

CREATE TABLE Child(id int IDENTITY(100,1));

GO

CREATE TRIGGER Parentins ON Parent FOR INSERT

AS

BEGIN

   INSERT Child DEFAULT VALUES

END;

GO

--End of trigger definition

SELECT id FROM Parent;
--id is empty.

SELECT id FROM Child;
--ID is empty. 

--Do the following in Session 1
INSERT Parent DEFAULT VALUES;
SELECT @@IDENTITY;
/*Returns the value 100. This was inserted by the trigger.*/

SELECT SCOPE_IDENTITY();
/* Returns the value 1. This was inserted by the
INSERT statement two statements before this query.*/ 

SELECT IDENT_CURRENT('Child');

/* Returns value inserted into Child, that is in the trigger.*/

SELECT IDENT_CURRENT('Parent');

/* Returns value inserted into Parent. 
This was the INSERT statement four statements before this query.*/ 

-- Do the following in Session 2.

SELECT @@IDENTITY;

/* Returns NULL because there has been no INSERT action
up to this point in this session.*/ 

SELECT SCOPE_IDENTITY();

/* Returns NULL because there has been no INSERT action
up to this point in this scope in this session.*/

SELECT IDENT_CURRENT('Child');

/* Returns the last value inserted into Child.*/