Sql server lock table while updating hot tub dating single
EDIT: Suppose the second query is This is really just the tip of the ice berg. In your example, nobody can answer your question about what is being actually locked because it will depend on many factors. These are bad practices because, among other things, they will lead exactly to lock contention. write locks you need to look into row versioning and snapshot isolation. So as originally posted: The quick and simple is "Yes, the first query will block the second query unless a specific index hint is specified ( NOLOCK, sometimes called a "dirty read" ) or the second query's transaction isolation level is set to IF NOT EXISTS ( SELECT 1 FROM sys.objects WHERE name = 'Foo' AND type = 'U' ) BEGIN --DROP TABLE dbo. Foo ( Foo_PK BIGINT IDENTITY( 1, 1 ) NOT NULL, PRIMARY KEY ( Foo_PK ), Bar BIT, x BIT, y BIT, z BIT ); CREATE NONCLUSTERED INDEX IX_Foo_x ON dbo. Foo ( Bar, x, y, z ) VALUES ( 1, 1, 1, 1 ), ( 0, 0, 0, 0 ); END; GO BEGIN TRANSACTION; UPDATE dbo.
Read Understanding Row Versioning-Based Isolation Levels. Foo SET y = 0 WHERE x = 1; -- COMMIT TRANSACTION; lock is range-specific, it also prevents other transactions from inserting or updating the affected columns by altering the data contained therein so that it could fall within that range of the original query.
In this tip, we will cover a scenario where we update statistics while the database is being used to see if blocking does occur during the statistics update.
This is a hot topic in the SQL Server DBA community.
Some people say that a statistics update blocks transactional activity.
As the lock itself being held is exclusive, the first query is preventing access to the resource from lock.
Now an edit for clarity: Unless I'm mistaken in what a dirty read is from the brief description of the risks mentioned here...In order to analyze the behavior of updating statistics, first we need to create a sample database with the option AUTO_UPDATE_STATISTICS set to OFF. Customers( Customer Id INT NOT NULL IDENTITY(1,1), Customer Code NVARCHAR(10) NOT NULL, Customer Name NVARCHAR(50) NOT NULL, Customer Address NVARCHAR(50) NOT NULL, Last Modified DATETIME NOT NULL DEFAULT GETDATE() PRIMARY KEY CLUSTERED (Customer Id), INDEX IX_Customer Code NONCLUSTERED (Customer Code) ) GO You can use Tibor Nagy's tip Populating a SQL Server Test Database with Random Data to fill the previous table with data.