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Does temp table improve performance?
Even if you can’t remove a temporary table, you may be able to drastically improve performance by making sure that the code that populates the temporary table is correctly filtering the data pulled from source tables.
Why is it sometimes better to use temporary tables as opposed to subqueries or derived tables?
In this case, a temporary table should be used since it guarantees that its values persist. is better with a derived table, because using a temporary table will require fetching all values from master , while this solution will just scan the first 100 records using the index on id .
Where does the temp table appear in a stored procedure?
The temp table (with single #) exists and is visible within the scope it is created (scope-bound). Each time you call your stored procedure it creates a new scope and therefore that temp table exists only in that scope.
Where are the table variables located in tempdb?
They reside in the tempdb database much like local SQL Server temp tables. Also like local SQL temp tables, table variables are accessible only within the session that created them. However, unlike SQL temp tables the table variable is only accessible within the current batch.
When to use CTEs instead of temp tables?
When you’re not sure what portions of the CTE’s data will actually be necessary for the rest of the query (because SQL Server can figure out what parts to execute, and what parts to simply ignore) When you need to break a query up into phases to isolate unpredictable components that dramatically affect the behavior of the rest of the query
When to use temporary tables vs.table variables?
However, unlike SQL temp tables the table variable is only accessible within the current batch. They are not visible outside of the batch, meaning the concept of session hierarchy can be somewhat ignored. As far as performance is concerned table variables are useful with small amounts of data (like only a few rows).