The forcetempkey function is used to abandon the database keys in a lookup and force the creation of a temporary key. This technique is valuable when the connection to the database is slow, and is enhanced when an equal join on an unfiltered column is requested. Under such circumstances, the joins are extremely fast. You do not have to specify the forcetempkey escape for equal and outer joins on columns without indexes. A temporary key join is performed automatically.

 

Example:

SELECT a.*, b.*
FROM db.dbo.tab a, db.dbo.tab b
WHERE
a.unique_key = b.unique_key
{forcetempkey} /* force the use of a temporary key (binary key is the default) */