What is computed column?
A computed column is a virtual column that is not physically stored in the table, unless the column is marked PERSISTED. A computed column expression can use data from other columns to calculate a value for the column to which it belongs.
How can you use computed column in an SQL query?
Go to your database, right click on tables, select “New Table” option. Create all columns that you require and to mark any column as computed, select that column and go to column Properties window and write your formula for computed column.
What can you do with persisted computed column?
Once you create a deterministic persisted computed column, it gives you additional flexibility. You can create indexes to optimize your queries and get an optimized execution plan. You can also create constraints such as Null, Check, Foreign key for persisted computed column.
When to update the Index on a computed column?
This means that the Database Engine stores the computed values in the table, and updates them when any other columns on which the computed column depends are updated. The Database Engine uses these persisted values when it creates an index on the column, and when the index is referenced in a query.
Is the computed column expression deterministic or persisted?
The computed_column_expression has no system data access or user data access. Any computed column that contains a common language runtime (CLR) expression must be deterministic and marked PERSISTED before the column can be indexed.
How to create indexes on Computed Columns in SQL Server?
You can create indexes to optimize your queries and get an optimized execution plan. You can also create constraints such as Null, Check, Foreign key for persisted computed column. You should refer to create indexes on SQL Server computed columns to explore indexing on computed columns in SQL Server.