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Can you make a computed column as persisted?
To be able to make a computed column as Persisted it has to be deterministic. Here are a few rules: If Persisted property is off then calculated column will be just a virtual column. No data for this column will be stored on disk and values will be calculated every time when referenced in a script.
Why are persisted columns used in floating point indexes?
Floating point indexes aside, persisted columns are pretty common. To some extent, this may be because inexperienced users assume that a computed column must always be persisted before it can be indexed. More experienced users may employ persisted columns simply because they have found that performance tends to be better that way.
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.
When to match back expressions to persisted columns?
Later in the compilation process (but still before even a trivial plan has been considered), the optimizer looks to match back expressions to persisted or indexed computed columns. The problem is that optimizer activities in the meantime may have changed the expanded expressions such that matching back is no longer possible.
How does the column collation work in SQL Server?
SQL Server implicitly converts the values to the collation of the column. The tempdb database is built every time SQL Server is started and has the same default collation as the model database. This is typically the same as the default collation of the instance.
How to specify the collation of a temporary table?
Specify that the temporary table column use the default collation of the user database, not tempdb. This enables the temporary table to work with similarly formatted tables in multiple databases, if that is required of your system. Specify the correct collation for the #TestTempTab column: