Is it necessary to use # for creating temp tables in SQL server?

Question

Is it necessary to use # before creating a temporary table in SQL server?

Example:

SELECT column1, column2, someInt, someVarChar  INTO ItemBack1  FROM table2 WHERE table2.ID = 7 

For ItemBack1 is it necessary to use the # symbol?

If not, then what is the use of # in creating temp tables?

Answer 1

Yes. You need to prefix the table name with "#" (hash) to create temporary tables.

If you do NOT need the table later, go ahead & create it. Temporary Tables are very much like normal tables. However, it gets created in tempdb. Also, it is only accessible via the current session i.e. For EG: if another user tries to access the temp table created by you, he'll not be able to do so.

"##" (double-hash creates "Global" temp table that can be accessed by other sessions as well.

Refer the below link for the Basics of Temporary Tables: http://www.codeproject.com/Articles/42553/Quick-Overview-Temporary-Tables-in-SQL-Server-2005

If the content of your table is less than 5000 rows & does NOT contain data types such as nvarchar(MAX), varbinary(MAX), consider using Table Variables.

They are the fastest as they are just like any other variables which are stored in the RAM. They are stored in tempdb as well, not in RAM.

DECLARE @ItemBack1 TABLE (  column1 int,  column2 int,  someInt int,  someVarChar nvarchar(50) );  INSERT INTO @ItemBack1 SELECT column1,         column2,         someInt,         someVarChar    FROM table2  WHERE table2.ID = 7; 

More Info on Table Variables: http://odetocode.com/articles/365.aspx