IDENTITY Property

SQLServerCentral Article

The IDENTITY Column Property

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There are a number of ways to generate key values in SQL Server tables including the IDENTITY column property, the NEWID() function and more recently, SEQUENCES. The IDENTITY column property is the earliest of these methods. It was introduced very early in the history of SQL Server and it is arguably the simplest approach. Though old, IDENTITY is still maintained in modern versions of SQL Server and is still relevant for simple use cases.

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2020-05-21

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Question of the Day

The Read Committed Snapshot Isolation behaviour

I am currently working with Sql Server 2022 and AdventureWorks database. First of all, let's set the "Read Committed Snapshot" to ON: 

use master;
go

alter database AdventureWorks set read_committed_snapshot on with no_wait;
go
Then, from Session 1, I execute the following code: 
--Session 1
use AdventureWorks;
go

create table ##t1 (id int, f1 varchar(10));
go

insert into ##t1 values (1, 'A');
From another session, called Session 2, I open a transaction and execute the following update: 
--Session 2
use AdventureWorks;
go

begin tran;
update ##t1 
set f1 = 'B'
where id = 1;
Now, going back to Session 1, what happens if I execute this statement? 
--Session 1
select f1
from ##t1
where id = 1;
 

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