Creating Clustered Index on a Table Variable column in MS SQL Server
If you need to create an index in order to improve performance of the queries running against table variable (@temptable) In MS SQL Server you can implicitly create a clustered index on a table variable by defining a primary key or unique constraint, however, it is generally more efficient to use a temporary table. Anyway let`s move on with an option of creating index on a table variable. For example, you need create simple table variable:
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Now you can select rows from temporary table using the command:
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If you turn on the option ‘Include Actual Execution Plan’, you will see next execution plan:
To create a clustered index on a table variable (@temptable) you should define a primary key on the ID column as shown below:
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Then you can check a new execution plan:
Now your queries ran against table variable will be faster and more efficient due using indexes.
Please don`t hesitate to ask question and put comments below.
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Utilizing given approach each client get his own database. In such case every client`s data stays isolated from others. It simplifies backing up the data, installing new clients but causes higher cost of maintenance.
Subject recursion is well covered in the literature, but, nevertheless, the problem of output “tree” does not mean the client and SQL Server many baffled. So, put the problem: there is a table with the name and record id field indicating the parent identifier. Immediately fill in this table, some sort of test data:
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