Difference
between Temp tables and Table variables in Sql Server
1)
Transaction
logs are not recorded for the table variables. They are variables and thus
aren't bound to a transaction.
Temp tables behave same as normal tables
and are bound by transactions.
2)
Any
procedure with a temporary table cannot be pre-compiled, while an execution
plan of procedures with table variables can be statically compiled in advance.
Pre-compiling a script gives a major advantage to its speed of execution. This
advantage can be dramatic for long procedures, where recompilation can be too
pricy.
3)
Table
variables exist only in the same scope as variables. Contrary to the temporary
tables, they are not visible in inner stored procedures and in exec (string)
statements. Also, they cannot be used in an insert/exec statement.
4)
As a
rule of thumb, for small to medium volumes of data and simple usage scenarios
you should use table variables.
5)
If we
use Temporary Table in a stored procedure, we should drop it at the end. It is
not necessary in the case of Table variable.
A simple example shows this difference quite
nicely:
GO
BEGIN TRAN
declare @var table (id int, data varchar(20) )
create table #temp (id int, data varchar(20) )
insert into @var
select 1, 'data 1' union all
select 2, 'data 2' union all
select 3, 'data 3'
insert into #temp
select 1, 'data 1' union all
select 2, 'data 2' union all
select 3, 'data 3'
select * from #temp
select * from @var
ROLLBACK
select * from @var
if object_id('tempdb..#temp') is null
select '#temp does not exist outside the transaction'
GO
We see
that the table variable still exists and has all it's data unlike the temporary
table that doesn't exists when the transaction rollbacked.
