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Performance Impacts of Computed Columns

Robert Sheldon takes us through a few scenarios:

In this article, I walk you through the process of applying these strategies so you have a better sense of the available options. For the examples, I created four similar tables and populated them with identical data, which comes from the WideWorldImporters sample database. Each table includes the same computed column, with the column persisted in two tables and indexed in two tables, resulting in the following mix:

– The Orders1 table includes a non-persisted computed column.
– The Orders2 table includes a persisted computed column.
– The Orders3 table includes an indexed, non-persisted computed column.
– The Orders4 table includes an indexed, persisted computed column.

For each table, I show you the execution plan that’s generated when querying the computed column. The column’s expression is a relatively simple one, and the data set very small. Even so, this should be enough to demonstrate the principles of creating persistent and indexed computed columns and how they can help address performance-related issues.

Click through for Robert’s results.

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