Sql Server SELECT INTO @variable?

sql

table-variables

temporary-tables

data-manipulation

byAlex Kataev·Aug 6, 2024

To assign a single value to a variable in SQL Server, you'd run:

DECLARE @MyVariable INT;     -- We're hiring an INT named @MyVariable 
SELECT @MyVariable = MyColumn FROM MyTable WHERE MyCondition; -- Gotcha! @MyVariable, you're assigned!

Be cautious! If MyCondition results in multiple rows, it will lead to errors. Use TOP 1 to avoid this confusion:

SELECT @MyVariable = TOP 1 MyColumn FROM MyTable ORDER BY SomeColumn; -- Dear @MyVariable, Meet the master of "MyColumn Got Talent!"

Here, @MyVariable successfully recruits the top performer from MyTable sorted by SomeColumn.

Applying SQL assignments with gusto

Tackling multiple variables like a boss

To assign multiple values to multiple variables, SQL Server is your go-to guy:

DECLARE @FirstName VARCHAR(50), @LastName VARCHAR(50); -- John Doe might be your name, but SQL Server sees you as @FirstName & @LastName!
SELECT @FirstName = FirstColumn, @LastName = LastColumn FROM PersonTable WHERE PersonID = 1; -- And the chosen one is...

Making table variables dance for you

Populating table variables? Sure! But remember to define their structure before they bust a move:

DECLARE @CustomerTable TABLE (CustomerID INT, CustomerName VARCHAR(255)); -- Who's the "ID", and who's the "Name" in @CustomerTable?
INSERT INTO @CustomerTable SELECT CustomerID, CustomerName FROM Customers WHERE Country = 'USA'; -- Come on, American customers! The stage is yours!

Temporary tables are here to party

If you have larger or more complex datasets, temporary tables will help you rock:

SELECT * INTO #MyTempTable FROM ExistingTable WHERE SomeCondition; -- #MyTempTable, don't wait! It's time to copy-paste the dance of ExistingTable!

Remember, these temporary tables have a lifespan bound to session scope, #TempTable, or even the entire SQL Server party, ##TempTable.

SQL selection patterns: Super Powers Unleashed!

Repeating table variables for maximum impact

Table variables are the ultimate tool for reducing database requests within a stored procedure:

SELECT ColumnNeeded FROM @MyTableVariable WHERE SomeOtherCondition; -- DJ @MyTableVariable on the decks, pumping out ColumnNeeded!

Temporary tables: not just a one-trick pony

Structural operations? Reporting? Analysis? Throw temporary tables into the mix:

CREATE TABLE #ComplexCalculations (Result INT); -- Give me that complex beat, #ComplexCalculations!
INSERT INTO #ComplexCalculations SELECT SUM(Value) FROM LargeDataSet GROUP BY Category; -- Adding some LargeDataSet seasoning to the beat

They're index-friendly and provide statistical analysis capabilities. Keep the party going with large datasets and temporary tables!

The magic wand: Single-statement execution

To minimize the risk of multiple-row returns while expecting a single value, consider:

DECLARE @MaxPrice MONEY;
SELECT @MaxPrice = MAX(Price) FROM Products WHERE IsActive = 1; -- Best price hunting season is open, @MaxPrice is the sniper!