Sometimes it's necessary to pass a list of values to stored procedures or functions.
User Role There is a limitation when indexing table variables.
Indexes can be created only in the table definition, moreover after declaration, table variables can't be altered.
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 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.
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.
If you've been a DBA for any amount of time I'm sure you've been asked the question: Which is better to use, a SQL Server temp table or a table variable?
There are technical reasons why to use one over the other, but being that I am usually just interested in performance I am more concerned with which one will be faster and use fewer resources.
Passing table variables as a parameter provides a flexible programming model and makes the process of passing the list of parameters to a stored procedure or a function easier and logically correct.