Top 15 differences between Temporary Tables and Table Variables in SQL Server: 1. EX: Open two SQL query window. It will delete once comes out the batch (Ex. If memory is available, both table variables and temporary tables are created. CTE is a named temporary result set which is used to manipulate the complex sub-queries data. More details. The temporary table only exists within the current transaction. I would like to know from the experts 1)when we should use a Temporary table, a Table variable and a Derived table ? 2)What are the limitations and advantages of each over the others? · This is not full info but i given as much as i covered, Temp tables, IO Operation - HIGH Explicit Indexing is allowed Constraints are allowed Need not create. Note the way you insert into this temp table. If you use a view, the results will need to be regenerated each time it is used. If the temporary table is large enough (more than 128 extents), the physical page deallocations are deferred, and performed by a background system task. Table variables are persisted just the same as #Temp tables. See answers from experts and links to MSDN, blogs, and other resources. (3) remember to drop temp tables as. Lifespan. SSC Guru. @tmp is a table variable. The scope of a local variable is the batch in which it is declared. 2. But table variables (since 2005) default to the collation of the current database versus temp tables which take the default collation of tempdb (ref). there is no data distribution of column values that exists for temporary tables. There's no hard and fast rule as to when a CTE (WITH) is better or performs better than a temp table. Temporary tables are similar to permanent tables, except temporary tables are stored in a TempDB and are deleted automatically when no longer in use. Table variable is a type of local variable that used to store data temporarily, similar to the temp table in SQL Server. amount from table ( GetFoo (123) ) foo_func, some_another_table foo2 where foo_func. May 22, 2019 at 23:59. Yet Another Temp Tables Vs Table Variables Article. A temporary table was created in PROC-A and he wanted to be able to use it in PROC-B and PROC-C. Differences between CTEs and Temporary Tables. A view, in general, is just a short-cut for a select statement. No difference. DECLARE @WordsToMatch TABLE (Word varchar(40)) --create a sample of words to. Only changing the table variables into temp tables ( out of the UDF, since #tables are not allowed ), decreases runtime significantly. Temp table's scope only within the session. Temp tables can be used in nested stored procedures. Now I have to replace Cursor with while loop but I am confused which is better to use temp table or table variable in loop to store data , from performance point of view. There was a request to make it possible to declare variables that are only visible within a block but Microsoft denied it. Temp Variables: Temp Variables are also used for holding the data fora temporary time just like Temp tables. In that sense, it would seem that it is fine to use nvarchar (max) in table variables instead of nvarchar (n), but. cas BETWEEN @Od AND @do in the last select. From the documentation. "##tempTable" denotes Global Temporary Tables. quantity < foo2. The peculiarities of table variables are as follows: A table variable is available in the. Temp tables are better in performance. INSERT. @Table Variables Do Not Write to Disk – Myth. they have entries in the system tables in tempDB, just like temp tables, and they follow the same behaviour regarding whether they are in memory or on disk. Only changing the table variables into temp tables ( out of the UDF, since #tables are not allowed ), decreases runtime significantly. The reason for the behavior is that SQL Server can't determine how many rows will match to ForeignKey, since there is no index with RowKey as the leading column (it can deduce this from statistics on the #temp table, but those don't exist for table variables/UDTTs), so it makes an estimate of 100,000 rows, which is better handled with a scan than a seek+lookup. B. After declaration, all variables are initialized as NULL, unless a value is provided as part of. If the Temporary Table is created in a Stored Procedure then it is automatically dropped on the completion of the Stored Procedure execution. SQL Server query engine internally creates the temp tables and the reason you provided above is not always true. Why Use Temporary Tables In Large Result Sets Whats The Gain. When temporary tables are estimating rows to read correctly, for the table variable the estimated row is just 100 and that eventually leads to an incorrect execution plan. temp table for batch deletes. soGlobalB table, one time, just as you would any traditional on-disk table. You are confusing two concepts. So for temporary data, you should use a temporary table. This simplifies query development and improves code readability and maintainability. #temp tables are stored on disk, if you're storing alot of data in the temp table. Local temporary tables (i. Because the CTEs are not being materialized, most likely. Table Variables - Not allowed. test_temp AS SELECT *. e. e. Gather similar data from multiple tables in order to manipulate and process the data. Local vs Global Temporary Tables. If the query is "long" and you are accessing the results from multiple queries, then a temporary table is the better choice. The consequences are evident: every query. 8. Temp tables are stored in TempDB. Global Temporary Table Table Variable: Common Table Expression – CTE: Scope:. g. You can compare two type of temporary tables: temp table vs temp table variable. Table Variables. Other ways how table variables differ from temp tables: they can't be indexed via CREATE INDEX, can't be created using SELECT/INTO logic, can't be truncated, and don't carry statistics. TempDB:: Table variable vs local temporary table. They have less overhead associated with them then temporary tables do. they have entries in the system tables in tempDB, just like temp tables, and they follow the same behaviour regarding whether they are in. We are finding on Azure that variant tables the query durations are considerably longer; very simple example; run 50 times each and averaged out. This is an improvement in SQL Server 2019 in Cardinality. Of course, you can place function into the package. More on Truncate and Temp Tables. The differences and similarities between table variables and #temp tables are looked at in depth in my answer here. Temp Tables supports non-clustered indexes and creates statistics on the query executed. Two-part question here. Temp Variables are created using a “DECLARE” statement and are assigned values using either a SET or SELECT command. A table variable is a local variable that has some similarities to temp tables. They are used most often to provide workspace for the intermediate results when processing data within a batch or procedure. 11. SQL Server, temporary tables with truncate vs table variable with delete. A table variable does not create statistics. You can compare two type of temporary tables: temp table vs temp table variable. In this article, you will learn the. TempVars is already declared and built in. Table variable is essentially a temporary table object created in memory and is always batch scoped. More actions. I would agree with this if the question was table variables vs. Very poor cardinality estimates (no statistics generated. Because a table variable might hold more data than can fit in memory, it has to have a place on disk to store data. 11. There was a request to make it possible to declare variables that are only visible within a block but Microsoft denied it. To reduce the impact on tempdb structures, SQL Server can cache temporary objects for reuse. At the time I suspected that the problem might have been related to the fact that table variables don't get statistics but I was dealing with something stupidly small like 15 rows and yet somehow using a physical temp table vs. Scope: Table variables are deallocated as soon as the batch is completed. Temporary tables can be accessed by multiple procedures or batches, while table variables are limited to the scope where they are declared. A temporary table is created and populated on disk, in the system database tempdb. Check related. I want to know why temp table can does truncate operation,but table variable doesn't? I hope the answer is from internal mechanism of truncate operation , or from the storage engine point, thank you. I have found temp tables much better than table variables and CTEs at many times but it is about testing the options you have and finding the best for you query. 1. Table variables don’t have the same magic ability to create column statistics on them that temp tables have. GCom = @GCom AND a. DECLARE @DETALLE TABLE ( FECHA smalldatetime, NO_OP NVARCHAR (100), MONTO FLOAT, PLAZO INT, CLIENTE NVARCHAR (100. Like with temp tables, table variables reside in TempDB. Each of these object groups will have one small table with only 2000 records and one larger one with 1000000 records so we can see if there. Should I use a #temp table or a @table variable? UPDATE: Truncate table won't work with declared table variable. Runtime with testdata is about 30 sec. A temporary table was created in PROC-A and he wanted to be able to use it in PROC-B and PROC-C. 1> :setvar tablename humanresources. A table variable temp can be referenced by using :temp. You should change the variable table to temporary temp table because variable table has a fixed value for cardinality estimate. There are three differences between a table and a table variable. 2. Usage Temp Table vs Table Variable. Best regards, Percy Tang. If does not imply that the results are ever run and processed. In a session, any statement can use or alter the table once it has been created:2 Answers. The temporary data stores tips included: temp tables , table variables , uncorrelated subqueries , correlated subqueries , derived tables , Common Table Expressions (CTEs) and staging tables implemented with permanent tables. Add your perspective Help others by sharing more (125 characters min. Now, instead of repeating the generation logic of my new column in all the three select statements, I thought of using a table variable to temporarily store the union results and add my column in a select from the table variable. This exists for the scope of statement. · The main difference between using a table. So why. In SQL Server, three types of temporary tables are available: local temporary tables, global temporary tables, and table variables. i. In that case, you don't need a temp table but a permanent table you just replace on the next run using the CREATE OR REPLACE TABLE statement. Temporary storage behaves in a rather unpredictable manner when utilized within the context of a parameterized stored procedure, the issue stems from a classic parameter sniffing and statistics miss-match problem that is regularly encountered when optimizing. I would summarize it as: @temp table variables are stored in memory. More so, the use-case of TEMP is in the local temporary tables, only visible to the current session. What you do with the temp tables is in fact caching the resultset generated by the stored procedures, thus removing the need to reevaluate. A temporary table can help in a few situations. Storage: There is a common myth that table variables are stored only in memory, but this is not true. #tmp is a temp table and acts like a real table mostly. 0?) and provide an alternative to temporary tables by allowing you to create a variable defined as type TABLE and then you can populate and use it in a variety of ways. 2 Answers. Neither of these are strictly true (they actually both go in tempdb, both will stay in memory if possible, both will spill to disk if required) – Damien_The_Unbeliever. How to create a virtual table in MS SQL. Without statistics, SQL Server might choose a poor processing plan for a query that contains a table variableFor more information on Common Table Expessions and performance, take a look at my book at Amazon. since Tempdb will be recreated from scratch ,after any reboot (using Model database as template) #temp will persist only for that session. 18. Table variables can be an excellent alternative to temporary tables. [SQL Server] — Temporary Tables vs Table Variables — Part 1. Also, temp tables should be local not global to separate processes don't affect each other . September 30, 2010 at 12:30 pm. A temporary table is created and populated on disk, in the system database tempdb. So Please clear me first what is virtaul table with example – 8. Temp Table. . The primary difference lies in the prefix you use: a single hash (#) for local temp tables and a double hash (##) for global temp tables. Simple approach 1: Try a primary key on your table valued variable: declare @temp table (a int, primary key (a)) Simple approach 2: In this particular case try a common table expression (CTE). But you would normally use a regular (#) temporary table here, not a global (##) temporary table. The differences between a temporary table and a database table are as follows: A temporary table data isn't stored in the database. . The results will vary on which will be easier to store the data, in disk (#temp) or in memory (@temp). At this point, both will now contain the same “new value” string. Starting SQL Server 2014, you can create nonclustered index inline while declaring the table variable. You can find the scripts that were used for the demonstration her. The objects created by users and user applications are called ‘user objects’ while the objects created by SQL Server engine as part of executing/processing the. However, > 100K is pretty broad, and contain millions or billions of rows. 983 Beginning execution loop Batch execution completed 1000 times. The TABLE keyword defines that used variable is a table. Temporary Object Caching. DECLARE @tv TABLE (C1 varchar (max), C2 varchar. The first difference is that transaction logs are not recorded for the table variables. A normal table will cause logging in your database, consume space, and require log flush on every commit. ). Table variables are preferable for small to medium-sized datasets and simple operations, especially when memory usage and logging overhead are concerns. There are also reasons for using temp tables instead of table variables. You could go a step further and also consider indexing the temp tables, something not possible with CTEs. These table variables are none less than any other tables as all table related actions can be performed on them. They are stored in tempdb in the same way as temporary tables, with the same allocation and deallocation mechanisms. Why would using a temp table vs a table variable improve the speed of this query? 1. Table variables are created using Declare statement. The following query is using table variables and temp tables, the following. Choosing Between Table Variables and Temporary Tables (ST011, ST012) Phil Factor demonstrates the use of temporary tables and table variables, and offers a few simple rules to decide if a table. Global temporary tables are useful in the (very rare) scenario where. · I want to know why temp table can does truncate. Problem 1 - User Defined Data Types If we use User Defined Data Types in our database design, sooner or later, will find that we cannot use them in temp tables. You can also refer the MSDN forum discussing the same; Maximum Capicity of Table Variable. "Temp Tables" (#) Vs. Table variables have a scope associated with them. Table variables are created in the tempdb database similar to temporary tables. After declaration, all variables are initialized as NULL, unless a value is provided as part of the declaration. หนึ่งในความสามารถของ SQL Server คือการที่เราสามารถสร้างตารางขึ้นมา เพื่อใช้แบบชั่วคราว (บางอย่างก็. You can force at least correct cardinality estimation using recompile option, but in no way can you produce column statistics, i. If you need to have the data for multiple statements -> then you need a temp table, since the CTE only exists for the next statement. You aren't even referencing the database. If a table variable is declared in a stored procedure, it is. If you have less than 100 rows generally use a table variable. In an example mentioned at the end of this article on SQL Server Central using 1 million rows in a table of each time, the query using the temporary table took less than a sixth of the time to complete. Aug 9, 2011 at 7:00. The following example will set a variable named tablename with the value of humanresources. Scope: Table variables are deallocated as soon as the batch is completed. In this SQL Server Quickie I'm talking about Temp Tables and Table Variables in SQL Server. That is one of the key reasons for using a temporary table. Temp tables have some issues around stored procedure compilation etc, but don't confuse these with table variables (the SQLCat articles mentions this). Table Variables. We can create indexes, constrains as like normal tables for that we need to define all variables. ; From your Transact-SQL, remove the create of the ##tempGlobalB table. 11. Regarding the two queries you have shown (unindexed table variable vs unindexed temp table) three possibilities spring to mind. Normally, we use temp tables in order to transform data before INSERT or UPDATE in the appropriate tables in time that require more than one query. Table variable starts with @ sign with the declare syntax. Local Temporary Tables. Check related question for more. 0?) and provide an alternative to temporary tables by allowing you to create a variable defined as type TABLE and then you can populate and use it in a variety of ways. SQL Server Table Setup for Performance Testing Temp Table vs Table Variable. – TheMet4lGod. Indexes. The code is composed of two halves that are nearly the same, except in the first half the table type is memory-optimized. The temp table names cannot exceed 116 characters whereas the permanent table can have 128 characters; The following example illustrates the transaction behavior in Temp tables:After declaring our temporary table #T and our table-variable @T, we assign each one with the same “old value” string. Have you really, honestly measured the. Foreign keys. Each type has its own characteristics and usage scenarios. E. In this article, you will learn about the main differences between Temp Table, Table variable and CTE. Local table variables are declared by using the DECLARE keyword. Table variables can have a primary key, but indexes cannot be created on them, neither are statistics maintained on the columns. We will see their features and how and when to use which one respectively. We are finding on Azure that variant tables the query durations are considerably longer; very simple example; run 50 times each and averaged out. They are not generally a replacement for a cursor. Table variables can lead to fewer stored procedure recompilations than temporary tables (see KB #243586 and KB #305977), and — since they cannot be rolled back — do not bother with the transaction log. Table variables are created using Declare statement. Not always. · I want to know why temp table can does truncate. Recompiles typically happen when the percentage of a tables (or temp tables) rows change by 500 and the cardinality (or. Table Variables can be seen as a alternative of using Temporary Tables. Some times, simply materializing the CTEs makes it run better, as expected. 1 Steps . However, if you keep the row-count low, it never materializes to disk. Scope: Local temporary tables ( #) are visible only to the session that creates them. This is because table variables are created in memory and do not require disk I/O. A table variable does not create statistics. table variable is created in the tempdb database but not the memory (entirely). This article explains two possible reasons to use a table variable rather than a temporary table. DECLARE @Groups table (DN varchar (256)) SELECT * FROM @Groups DECLARE @SQL varchar ( MAX) SET @SQL = 'SELECT * FROM OpenQuery ()' PRINT @SQL Insert Into @Groups EXEC (@SQL) SELECT * FROM @Groups. Since @table variables do not have statistics, there is very little for the optimizer to go on. That's one reason why Microsoft provided a table variable as an alternative to temp tables, so it can be used in scenarios where it is considered beneficial to keep a fixed plan. Temp Variables in SQL Server. There are no statistics created on table variables and you cannot create statistics. That’s wrong; they’re all backed by temporary objects, and may very well spill to disk when you run of of scratch space. (This is because a table. A table variable cannot change its definition. CREATE TABLE #LocalTempTable ( ID INT PRIMARY KEY, Name VARCHAR ( 50 ), Age INT ); Local temporary tables are only visible to the session in which they are created. They do allow indexes to be created via PRIMARY KEY. com: Common Table Expressions Joes 2 Pros®: A CTE Tutorial on Performance, Stored Procedures, Recursion, Nesting and the use of Multiple CTEs There are many reasons that a Temp Table, Table Variable or Common Table. TRUNCATE deallocates the last page from the table and DELETE doesn't. They will be cleared automatically at the end of the batch (i. In SQL Server 2016 parallel inserts are also supported into temp tables that are heaps. The ability to create a PK on a #temp or table variable gives the query optimizer more information than a CTE (as you cannot declare a PK on a CTE). One of the comments suggested comparing these results to using a Common Table Expression (CTE) for similar operations. Both are in TempDB (to dispel some myths) but: By default temp tables have the statistics while for tables variables the engine always estimates 1 row (also with InMemory option). Instead of dropping a temporary object, SQL Server retains the system metadata, and truncates the table data. We saw two reasons for using table variables rather than temp tables. And you can't use your own variables in expressions like you can use the built in tempvars say in sql expressions. temp table for batch deletes. These little buggers have so many issues, it’s hard to know where to begin. The only time this is not the case is when doing an insert and a few types of delete conditions. Sorted by: 2. Share. I have to write a table function so I prototyped the query in SQL Server and used a temp table but when I change it to a table variable the query goes from taking approx. Then, the result is joined to various table to get the request data. Temporary tables, on the other hand, are more suitable for larger datasets and complex operations. When to Use Table Variables vs. when you don't need indexes that are present on permanent table which would slow down inserts/updates) Share. Table variables have a well defined scope. For example, a stored procedure might store intermediate results in a temporary table and process them for better performance. ago. The basic syntax for creating a global temporary tableis almost identical to creating a Local Temporary SQL table. ;with temp as ( SELECT a as Id FROM BigTable WHERE someRecords like '%blue' ), UPDATE AnotherBigTable SET someRecords =. A CTE, while appearing to logically segregate parts of a query, does no such thing. If memory is available, both table variables and temporary tables are created and processed. Temp tables can be used in nested stored procedures. @Result = 0 RETURN @Result END ELSE BEGIN SET @Result = 1 SELECT * FROM @tmp_Accounts END. By a temporary data store, this tip means one that is not a permanent part of a relational database or a data warehouse. The best practice is use #temp_table for large sets of data and @tableVariable for small datasets. Unlike a temporary table, a table variable has a limited scope and is not visible to other sessions or transactions. department 1> select * from $ (tablename) 2> go. Share. PossiblePreparation • 4 yr. In this section we will cover each of these concepts. [MainView] AS SELECT. After declaration, all variables are initialized as NULL, unless a value is provided as part of the declaration. myTable. Learn the pros and cons of using temp tables and table variables in SQL Server, such as performance, indexing, transactions, collation, and usage scenarios. Cursors work row-by-row and are extremely poor performers. #mytable is a temporary table where as mytable is a concrete table. For this test scenario we are going to load data into four tables, two will be temporary tables and two will be table variables. Temp tables vs variable tables vs derivated table vs cte. There is a great answer here with lots of specifics as to where they are different. Execution plan for the table variable version Execution plan for the temp table versionThere are many similarities between temp tables and table variables, but there are also some notable differences. Table Variable. You can use a temporary table just like you use a database table. department 1> select * from $ (tablename) 2> go. ). Specifically in your case I would guess that the fact that temp tables can have additional statistics generated and parallel plans while table variables have more limited statistics (no column level. During low volume periods, we have an agent job to remove older rows to keep the tables size in check. Most of the time I see the optimizer assume 1 row when accessing a table variable. 2nd Method - Use Global Temp Table:When using temp tables within stored procedures, this can be a disadvantage. It is important to create the memory-optimized table at deployment time, not at runtime, to. May 23, 2019 at 0:15. g. CREATE TABLE: You will create a table physically inside the database. There are times when the query optimizer does better with a #temp compared to a table variable. Temp tables may be a better solution than table variables when it is possible for the rowcount to be larger (greater than 100). There are two varieties of temp tables. So we have the query with the table variable generating an execution plan that results in nearly 20,000 seeks against an index vs. Snivas, You are correct about temporary tables being stored in the tempdb and for the most part table variables are stored in memory, although data can be stored in the tempdb if needed (low memory) then the tempdb acts like a page file. The first type of table is the temporary table (or “Temp Table”) and it behaves to all intents and purposes like a normal SQL table with the only difference that it is stored in the TEMPDB system database . dbo. Temporary table vs short-circuit operation for SQL query. Once SQL Server finishes a transaction (with the GO or END TRANSACTION. The Sp was earlier using Cursors in it. There is a difference. it assumes 1 row will be returned. They will be cleared automatically at the end of the batch (i. #Temp tables are just regular SQL tables that are defined and stored in TempDB. We can create indexes that can be optimized by the query optimizer. The biggest difference between the two are that statistics are available for temporary tables while. A Temporary table differs in the following two ways from regular tables: Each temporary table is implicitly dropped by the system. Temp variable can only have 1 index i. Temp table starts with one # in front of table name is local temp table and with two ## is global temp table. This query was passed to me by a colleague to see if I could figure out what was happening, but I'm pretty stumped. In order to avoid duplication I want to use temp tables instead (not table variable, which does not bring advantages that I seek - inferred type). You cannot use a temp table in any way inside a user-defined function. IT depends on lot more other factors like Indexes,Fragmentation,Statastics etc. Temporary Table vs Table Variable Performance within Stored Procedures. The real answer to knowing the difference lies in what is going on under the hood and correlating those specifics to. SELECT CommonWords. The TABLE keyword defines that used variable is a table. Namely, temp tables can be altered with DDL statements but table variables can't (so you cannot create a nonclustered index on a table variable for example). Index large reporting temp tables. Because a table variable might hold more data than can fit in memory, it has to have a place on disk to. 7. Learn the differences between temp tables and table variables in SQL Server, such as storage location, lifetime, visibility, object metadata, and more. In a previous article, SQL Server Temp Table vs Table Variable Performance Testing, we looked at SQL Server performance differences between using a temp table and a table variable for different DML operations. The table variable doesn't. t. I want to know why temp table can does truncate operation,but table variable doesn't? I hope the answer is from internal mechanism of truncate operation , or from the storage engine point, thank you. Like with temp tables, table variables reside in TempDB. The Syntax of creating a Table Variable is close to creating a normal table but since it is a variable, so we declare a Table Variable. Global temporary tables (CREATE TABLE. However, they have some major limitations as listed below. This is because SQL Server won't create statistics on table variables. A temp table remain until the instance is alive or all sessions are closed depending upon the type of the temp table (local or global temp table) A temporary variable remains only for any particular batch execution in which it is created. This is an improvement in SQL Server 2019 in Cardinality. The temp table will be stored in the tempdb. @ = User-defined Table Variable User-defined Table Variables were introduced in SQL Server 2000 (or, wow – was it 7. I find the temp table faster. I prefer use cte or derivated table since ram memory is faster than disk. they have entries in the system tables in tempDB, just like temp tables, and they follow the same behaviour regarding whether they are in memory or on disk. Temporary Tables are real tables so you can do things like CREATE INDEXes, etc. A query that modifies table variables will not contain any parallel zones. On the other hand, using a CTE is much easier and less cumbersome than setting up, filling,. Those options are CTEs, Temp Tables and Table Variables. 1 . I use a #temp table or a @table variable? talks more about how to use them. I am trying to run this from a table function hence the need for the table variable as opposed to the temp table. Temp table can be used when you are dealing with a lot more data which will benefit from the creation of indexes and statistics. See examples, diagrams, and links to related questions and. Other ways how table variables differ from temp tables: they can't be indexed via CREATE INDEX, can't be created using SELECT/INTO logic, can't be truncated, and don't carry statistics. There is a performance difference that favors table variables because temporary tables prevent precompilation of procedures. Thanks. No, you cannot "return" a temp table - you can create that temp table before calling your function, and have your function write data into that temp table. This helps because it allows you to move objects (tables, procedures) to other locations without having to change the existing objects that reference them. How to decide what to use temporary table or table variable in a stored procedure where both serves the purpose? Anujit Karmakar Sr. WITH defines a common table expression (CTE) used within a single query. e. This article explains the differences,. 6. When deciding between temp tables and table variables, there are several factors to consider, such as the size and complexity of the data you need to store and process, the frequency and duration. (2) test the option to create the table fist and use INSERT INTO instead of SELECT INTO. table is primarily used for temporarily storing a set of rows that are returned as the table-valued function result set. I have an UDF, providing a bunch of data. If a table variable is declared in a stored procedure, it is. Please check the below code which I will use to create Temp Table and Variable Table. The time to take inserting that data gets to be pretty long. I have a big user defined table type variable having 129 Columns. 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. Both table variables and temp tables are stored in tempdb. You materialize the output so it is only executed once. At the bottom of the post there are the prerequisites for using. I did not find the answer. Faster because the table variable is stored in memory. Meanwhile, the WITH clause acts as a temporary table, but it is actually a result of a subquery which can be used somewhere else. Without ever looking, I'd expect global temp table creation to require more log records than local temp table, and local temp table to require more than table variable…1 Answer.