Microsoft SQL Server Variables Declare a Table Variable

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Example

DECLARE @Employees TABLE
(
    EmployeeID INT NOT NULL PRIMARY KEY,
    FirstName NVARCHAR(50) NOT NULL,
    LastName NVARCHAR(50) NOT NULL,
    ManagerID INT NULL
)

When you create a normal table, you use CREATE TABLE Name (Columns) syntax. When creating a table variable, you use DECLARE @Name TABLE (Columns) syntax.

To reference the table variable inside a SELECT statement, SQL Server requires that you give the table variable an alias, otherwise you'll get an error:

Must declare the scalar variable "@TableVariableName".

i.e.

DECLARE @Table1 TABLE (Example INT)
DECLARE @Table2 TABLE (Example INT)

/*
-- the following two commented out statements would generate an error:
SELECT *
FROM @Table1
INNER JOIN @Table2 ON @Table1.Example = @Table2.Example

SELECT *
FROM @Table1
WHERE @Table1.Example = 1
*/

-- but these work fine:
SELECT *
FROM @Table1 T1
INNER JOIN @Table2 T2 ON T1.Example = T2.Example

SELECT *
FROM @Table1 Table1
WHERE Table1.Example = 1


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