David Bird


Technical Article

Compare the Data in Two Tables

These queries are used to compare the data in two tables.   In these examples all the rows in each table is retrieved and compared using the UNION ALL command.  I would recommend adding additional WHERE criteria for very large tables to reduce the number of rows that will be compared.These SQL statements are based on […]

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2007-08-09 (first published: )

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Technical Article

Shrink Log file for all Databases

I use this script to shrink the log files for development databases. The intention is keep the log files as small as possible when the database is not in use. By scheduling this script I can control when it happens as oppose to using auto shrink.

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2005-07-08 (first published: )

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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;
 

See possible answers