MSSQL - Understanding Isolation Level by Example (Read Uncommitted)

Example SQL Statements below used in the video, you can Copy and Paste for Transaction Isolation Level of Serializable, Read Committed, Read Uncommitted, Repeatable Read --===================================== -- Windows/Session #1 --===================================== IF EXISTS (SELECT 1 FROM sys.tables WHERE name = 'SampleTable') DROP TABLE SampleTable CREATE TABLE [SampleTable] ( [Id] [int] IDENTITY(1,1) NOT NULL, [Name] [varchar](100) NULL, [Value] [varchar](100) NULL, [DateChanged] [datetime] NULL, CONSTRAINT [PK_SampleTable] PRIMARY KEY CLUSTERED ([Id] ASC) ) INSERT INTO SampleTable(Name, Value) SELECT 'Name1', 'Value1' UNION ALL SELECT 'Name2', 'Value2' UNION ALL SELECT 'Name3', 'Value3' SELECT * FROM SampleTable BEGIN TRAN INSERT INTO SampleTable(Name, Value) VALUES('Name4', 'Value4') --UPDATE SampleTable SET Name = Name + Name --UPDATE SampleTable SET Name = Name + Name WHERE Name = 'Name1' UPDATE SampleTable SET Name = Name + Name WHERE ID = 1 WAITFOR DELAY '00:02:00' ROLLBACK --===================================== -- Windows/Session #2 --===================================== --------------------------------------------------- -- This window/session is default READ COMMITTED -- --------------------------------------------------- SELECT * FROM SampleTable SELECT * FROM SampleTable WITH (NOLOCK) SELECT * FROM SampleTable WHERE ID = 3 SELECT * FROM SampleTable WHERE Name = 'Name2' SELECT b.name, c.name, a.* FROM sys.dm_tran_locks a INNER JOIN sys.databases b ON a.resource_database_id = database_id INNER JOIN sys.objects c ON a.resource_associated_entity_id = object_id --===================================== -- Windows/Session #3 --===================================== ----------------------------------------------------- -- This window/session is default READ UNCOMMITTED -- ----------------------------------------------------- SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED SELECT * FROM SampleTable SELECT * FROM SampleTable SELECT * FROM SampleTable WHERE ID = 2 SELECT * FROM SampleTable WHERE Name = 'Name2' SELECT * FROM SampleTable WITH (NOLOCK)