Execution Plan

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Plansplaining, part 20. SQL Graph (part 1)

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Welcome to part twenty of the plansplaining series. It has been a long time since I last wrote a plansplaining post, partly because of my health, but also for a large part because I was out of ideas. But recently I decided to dig a bit deeper into a feature that was released in SQL Server 2017 and that I had so far not played with: SQL Graph.

2023-12-06

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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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