Updating table variables sql 2016 examples of good profiles for dating sites
SQL Server 2014 In addition to the methods of adding constraint based indexes discussed below SQL Server 2014 also allows non unique indexes to be specified directly with inline syntax on table variable declarations. /*SQL Server 2014 compatible inline index syntax*/ DECLARE @T TABLE ( C1 INT INDEX IX1 CLUSTERED, /*Single column indexes can be declared next to the column*/ C2 INT INDEX IX2 NONCLUSTERED, INDEX IX3 NONCLUSTERED(C1, C2) /*Example composite index*/ ); Filtered indexes and indexes with included columns can not currently be declared with this syntax however SQL Server 2016 relaxes this a bit further.
From CTP 3.1 it is now possible to declare filtered indexes for table variables. Traditional tables in SQL Server can either have a clustered index or are structured as heaps.
There is a cost in creating both kinds of temp tables; and if you have so much data in that that you need an index it might be time to look at using a real table; that you set up to be transaction safe; filter by spid or user id and then clear it down at the end.
Real tables v temp tables both have their ups and downs but if performance is an issue; try it with a real table too.
Contents Caveat This answer discusses "classic" table variables introduced in SQL Server 2000.
SQL Server 2014 in memory OLTP introduces Memory-Optimized Table Types. Both are stored in tables but table variables can use them from the current database (Source). As Aaron points out in the comments the behavior of temporary tables in these differs ) or when the session ends otherwise.
In-Memory OLTP, also known as ‘Hekaton’ and ‘In-Memory Optimization’, is Microsoft’s latest in-memory processing technology.A common misconception is that this is not the case for table variables so a script demonstrating this is below, it declares a table variable, adds a couple of rows then updates them and deletes them.Because the table variable is created and dropped implicitly at the start and the end of the batch it is necessary to use multiple batches in order to see the full logging. Ideally should be no concurrent activity at all */ CHECKPOINT; GO /* The 2nd column is binary to allow easier correlation with log output shown later*/ DECLARE @T TABLE ([C71ACF0B-47E9-4CAD-9A1E-0C687A8F9CF3] INT, B BINARY(10)) INSERT INTO @T VALUES (1, 0x41414141414141414141), (2, 0x41414141414141414141) UPDATE @T SET B = 0x42424242424242424242 DELETE FROM @T /*Put allocation_unit_id into CONTEXT_INFO to access in next batch*/ DECLARE @alloc Id BIGINT, @Context_Info VARBINARY(128) SELECT @Context_Info = allocation_unit_id, @alloc Id = a.allocation_unit_id FROM sys.system_internals_allocation_units a INNER JOIN sys.partitions p ON p.hobt_id = a.container_id INNER JOIN sys.columns c ON c.object_id = p.object_id WHERE ( = 'C71ACF0B-47E9-4CAD-9A1E-0C687A8F9CF3' ) SET CONTEXT_INFO @Context_Info /*Check log for records related to modifications of table variable itself*/ SELECT Operation, Context, Alloc Unit Name, [Row Log Contents 0], [Log Record Length] FROM fn_dblog(NULL, NULL) WHERE Alloc Unit Id = @alloc Id GO /*Check total log usage including updates against system tables*/ DECLARE @alloc Id BIGINT = CAST(CONTEXT_INFO() AS BINARY(8)); WITH T AS (SELECT Operation, Context, CASE WHEN Alloc Unit Id = @alloc Id THEN 'Table Variable' WHEN Alloc Unit Name LIKE 'sys.%' THEN 'System Base Table' ELSE Alloc Unit Name END AS Alloc Unit Name, [Log Record Length] FROM fn_dblog(NULL, NULL) AS D) SELECT Operation = CASE WHEN GROUPING(Operation) = 1 THEN 'Total' ELSE Operation END, Context, Alloc Unit Name, [Size in Bytes] = COALESCE(SUM([Log Record Length]), 0), Cnt = COUNT(*) FROM T GROUP BY GROUPING SETS( ( Operation, Context, Alloc Unit Name ), ( ) ) ORDER BY GROUPING(Operation), Alloc Unit Name can work out better anyway) Cardinality Many of the execution plans involving table variables will show a single row estimated as the output from them.Clustered indexes can either be declared as unique to disallow duplicate key values or default to non unique.If not unique then SQL Server silently adds a uniqueifier to any duplicate keys to make them unique.