How to create temperory tables in sqlserver and how to insert and how to select

DECLARE @ProductTotals TABLE

(

  ProductID int,

  Revenue money

)

INSERT INTO @ProductTotals (ProductID, Revenue)

  SELECT ProductID, SUM(UnitPrice * Quantity)

    FROM [Order Details]

    GROUP BY ProductID

select * from @ProductTotals

While connected to the Northwind data-base, we could write the following SELECT statement to populate the table variable.  

You can use table variables in batches, stored procedures, and user-defined functions (UDFs). We can UPDATE records in our table variable as well as DELETE records

UPDATE @ProductTotals

  SET Revenue = Revenue * 1.15

WHERE ProductID = 62

DELETE FROM @ProductTotals

WHERE ProductID = 60

SELECT TOP 5 *

FROM @ProductTotals

ORDER BY Revenue DESC

You might think table variables work just like temporary tables (CREATE TABLE #ProductTotals), but there are some differences.