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Is table variable faster than temp table?
Whereas, a Temporary table (#temp) is created in the tempdb database. So table variable is faster then temporary table. ⇒ Temporary tables are allowed CREATE INDEXes whereas, Table variables aren’t allowed CREATE INDEX instead they can have index by using Primary Key or Unique Constraint.
What is an advantage of table variables over temporary 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. They are not visible outside of the batch, meaning the concept of session hierarchy can be somewhat ignored.
Which one is better temp table or table variable?
A temp table can have indexes, whereas a table variable can only have a primary index. If speed is an issue Table variables can be faster, but obviously if there are a lot of records, or the need to search the temp table of a clustered index, then a Temp Table would be better.
What is the difference between cursor temp table and table variable?
Temp Tables are physically created in the tempdb database. Table Variable acts like a variable and exists for a particular batch of query execution. It gets dropped once it comes out of a batch. This is also created in the tempdb database but not the memory.
Why is there such big difference using table variables vs.temp tables?
But suprisingly just using #temp table instead of @temp variable made the execution slow again. I was suprised to see such differences using or not-using temp table/variable. Appearently SQL Server could not by itself optimize the insides of the OUTER APPLY clause. But why there is such a big difference using table variables vs. temp tables?
Why is SQL Server insert into temp table slow?
I think the problem lays in the temp table insert. I did try to apply an index to the temp table but this will only reduce performance as: The number of indexes on a table is the most dominant factor for insert performance. The more indexes a table has, the slower the execution becomes.
How to optimize temp table and table variables?
If you use temporary tables, table variables, or table-valued parameters, consider conversions of them to leverage memory-optimized tables and table variables to improve performance. The code changes are usually minimal. Scenarios which argue in favor of conversion to In-Memory. Technical steps for implementing the conversions to In-Memory.
Why does query optimizer sometimes generate poor execution plans?
The reason is that the query optimizer will sometimes generate poor plans for table vars. This can mostly be seen when there is a lot of data. The biggest point I can make is that table variables are more likely to cause unpredictable execution plans when compared to the plans generated for temp tables.