Showing posts from November, 2015

Temp Tables vs Table Varibles: The Great Debate

There seems to be a lot of confusion around the differences between  temp tables and table variables (in the classic sense; I'm not talking about in memory table types or anything here). Some people say you should only use table variables. Some people say you should only use temp tables. Most people caution a more nuanced approach. Here I want to cover what I think are the biggest issues in an attempt to shed some light on this surprisingly tricky topic.

Statistics This is usually the most important factor when considering which one to use. It boils down to two facts, and everything else flows from these: Temp Tables maintain statistics, Table Variables do not.

Table Variables Because table variables maintain no statistics, the Query Optimizer always assumes the contain exactly one row. As a result, any joins against a table variable, unless explicitly told to behave otherwise will (probably) alwaysbe a nested loop join.

As long as the number of rows in the table variable are small…

Database Size Script

This is just a fancier version of sp_spaceused which writes the data to a temp table which you can sort on use ManGroup set nocount on go declare @TableName varchar(128), @RID int, @MaxRID int, @SQL nvarchar(max) if object_id('tempdb.dbo.#LoopSrc') is not null drop table #LoopSrc create table #LoopSrc ( RID int identity(1,1) primary key clustered, TableName varchar(128) ) if object_id('tempdb.dbo.#Tabs') is not null drop table #Tabs create table #Tabs ( TableName varchar(128), nRows int, nReserved as cast(replace(sReserved, ' KB', '') as int), nData as cast(replace(sData, ' KB', '') as int), nIndexSize as cast(replace(sIndexSize, ' KB', '') as int), nUnused as cast(replace(sUnused, ' KB', '') as int), sReserved varchar(30), sData varchar(30), sIndexSize varchar(30), sUnused varchar(30) ) /***************************** *** INSERT LOOP ITE…