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Do you have to persist Computed Columns in SQL?
There are three important caveats to this: The computed column must be persisted. Even if indexed, the column must also be persisted. Match back from general query expressions to persisted computed columns is disabled. The documentation does not describe the function of the trace flag, and does not prescribe it for any other use.
When to mark a computed column as persisted?
Marking a computed column as PERSISTED allows an index to be created on a computed column that is deterministic, but not precise. For more information, see Indexes on Computed Columns. Any computed columns used as partitioning columns of a partitioned table must be explicitly marked PERSISTED.
When to use persisted property in SQL Server?
You may have noticed that we also used the property “Persisted” for our computed column. This property for computed columns has been introduced in SQL Server 2005 and onwards. It is important for any computed column, because many additional features depend on it. To be able to make a computed column as Persisted it has to be deterministic.
Why are columns not marked persisted in SQL?
Often such columns cannot be marked as persisted because the functions are deemed to be non-deterministic; though this can be defeated for some functions that actually are deterministic by using WITH SCHEMABINDING. Consider the following two nearly identical functions:
Are there any Computed Columns with scalar functions?
In SQL Server, Computed Columns and User Defined Scalar Functions don’t always get along nicely. Most database developers complain about the performance of Computed Columns that use a Scalar Function to determine its value. In this tip, we will investigate the secret behind this bad relationship.
Are there any Computed Columns in SQL Server?
In SQL Server, Computed Columns and User Defined Scalar Functions don’t always get along nicely. Most database developers complain about the performance of Computed Columns that use a Scalar Function to determine its value.
How often to call scalar function in SQL Server?
The Scalar-valued function will be executed once for each row in the result set, where SQL Server will call the Table-valued function once regardless of the number of rows to be processed.