Updating table variables sql 2016
In queries where table variables are referenced outside a FROM clause, they must be referenced by an alias as shown below: --Declaring table variable DECLARE @user Role List User Role SELECT url. Role ID --Is referenced using an alias FROM @user Role List url --Alias for table variable must be defined, when referenced outside a FROM clause INNER JOIN dbo. They have many features of regular tables such as indexes, constraints, computed columns, etc.
However, they have some restrictions: they can't be altered after creation, statistics are not maintained, etc.
Phil Factor (real name withheld to protect the guilty), aka Database Mole, has 30 years of experience with database-intensive applications.
Despite having once been shouted at by a furious Bill Gates at an exhibition in the early 1980s, he has remained resolutely anonymous throughout his career.
Test Table AS TABLE ( ID INT, Name NVARCHAR(40) ) --Declaring table variable DECLARE @Test Table AS dbo.
Test Table --Inserting data into table variable INSERT INTO @Test Table(ID, Name) VALUES(1, 'Abc') There is a common misconception that table variables are in memory objects.
User Role AS target USING @p User Role List AS source ON target. In the following code we illustrate the call of our stored procedure with a table-valued parameter: --Table before update SELECT * FROM dbo.
User Role --Declaring table variable DECLARE @user Role List User Role --Generating updated data INSERT INTO @user Role List(User ID, Role ID) VALUES (1,4), (5,5) --Applying new user-role mapping update EXEC usp Update User Role Mapping @[email protected] --Table after update SELECT * FROM dbo.
Phil Factor demonstrates the use of temporary tables and table variables, and offers a few simple rules to decide if a table variable will give better performance than a temp table (ST011), or vice-versa (ST012). Phil Factor (real name withheld to protect the guilty), aka Database Mole, has 30 years of experience with database-intensive applications.There are some features in SQL Server which allow developers to work with temporary data. It has been improved in SQL Server version by version and in SQL Server 2014 it has become quite flexible.To work with table variables more confidently and to be able to identify the appropriate tasks they can be applied to, we need to fully understand table variables, their features, limitations, restrictions and application areas.In reality they are stored in the tempdb database like temporary tables.Like regular variables, table variables are visible only within the batch where they were created.