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Posted by / 29-Jul-2020 15:22

Updating table variables sql 2016

Like regular variables they are not affected by rollback in transactions which could be a big plus depending on your requirements.Review these tips for more information: Sergey Gigoyan is a database professional with more than 10 years of experience, with a focus on database design, development, performance tuning, optimization, high availability, BI and DW design.A table variable is a variable data type which can be used to store temporary data.It's defined using the DECLARE keyword and the table's structure is defined in the declaration as shown below: --Creating User Defined Table Type CREATE TYPE dbo.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.Starting with SQL Server 2014, non-unique and composite indexes can be created. --Declaring table variable with primary key DECLARE @Test Table1 TABLE ( ID INT PRIMARY KEY, Name NVARCHAR(40) ) --Declaring table variable with unique key DECLARE @Test Table2 TABLE ( ID INT PRIMARY KEY , Name NVARCHAR(40) UNIQUE ) --Declaring table variable with unique clustered index DECLARE @Test Table3 TABLE ( ID INT PRIMARY KEY NONCLUSTERED, Name NVARCHAR(40) UNIQUE CLUSTERED ) --Declaring table variable with nonclustered, non-unique index ( Starting from SQL Server 2014 ) DECLARE @Test Table3 TABLE ( ID INT PRIMARY KEY, Name NVARCHAR(40), INDEX IX_Test Table3_Name NONCLUSTERED (Name) ) --Declaring table variable with composite nonclustered index ( Starting from SQL Server 2014 ) DECLARE @Test Table4 TABLE ( ID INT PRIMARY KEY, First Name NVARCHAR(40), Last Name NVARCHAR(40), INDEX IX_Test Table4_First Name_Last Name NONCLUSTERED (First Name, Last Name) ) --Declaring table variable with more than one index ( Starting from SQL Server 2014 ) DECLARE @Test Table5 TABLE ( ID INT PRIMARY KEY, First Name NVARCHAR(40), Last Name NVARCHAR(40), INDEX IX_Test Table5_First Name NONCLUSTERED (First Name), INDEX IX_Test Table5_Last Name NONCLUSTERED (Last Name) ) It's important to know the table variable restrictions and limitations when working with them.One of these restrictions has been already mentioned above: table variables can't be altered after creation, so we should consider this fact and choose the right structure for the table variable and create the necessary indexes and constraints in the table definition.

User Role (User ID, Role ID) VALUES (1,2),(2,5),(3,2),(4,6) CREATE PROCEDURE usp Update User Role Mapping @p User Role List User Role READONLY AS BEGIN MERGE dbo. Table variables must be passed as READONLY and we can't perform DML operations (INSERT, UPDATE, DELETE) on a table variable in the body of stored procedure or function.Secondly, SQL Server doesn't maintain statistics for table variables, so to improve performance, it is suggested to use temporary tables instead of table variables when working with large temporary data set.CHECK and DEFAULT constraints, COMPUTED COLUMNS can be created on table variables (in the table definition), however unlike regular tables we can't use user-defined functions in their definition.We can't use SELECT INTO or INSERT EXEC statements to initialize a table variable.Table variables can be passed to stored procedures and functions only as READONLY. User ID --Is referenced using an alias Table variables are a good solution for working with small temporary data, also they allow us to pass a list of values to stored procedures and functions which makes some development needs much simpler.

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These kind of tasks can be solved by using an input parameter as an XML type, but this is not a perfect solution, because it requires additional work (XML has to be parsed in the stored procedure).

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