Tsql update computed column

Now you need to go to the column properties that will be available at the bottom right and edit the formula as shown below. Step 3 : Now, it seems that we just need to press the save button and SSMS will alter the computed column without dropping it. But hang on a second, instead of pressing the save button , press the generate script button to see what changes SSMS will implement in case of pressing save button.

However, once you press generate script button it will pop up save change script window to show you the changes as shown below. Given below is the complete script I copied from the generate script window for your reference that will be implemented once you press the save button. As you can see, SSMS will create a temporary table with the correct computed column formula, then migrate all the data and drop the old table and rename the temporary table to the old table name.

And in this case, it drops the computed column and table as well. Conclusion : As you can see in both methods, you need to drop and recreate the computed column in order to alter it. Comments RSS. You are commenting using your WordPress. You are commenting using your Google account.

Because each row in a table can have different values for columns involved in a computed column, the computed column may not have the same result for each row. For more information, see Indexes on Computed Columns. Constraint names must follow the rules for identifiers , except that the name cannot start with a number sign.

User-specified fillfactor values can be from 1 through If a value is not specified, the default is 0. For example, in the AdventureWorks database, the ProductVendor table has a referential relationship with the Vendor table. The ProductVendor. BusinessEntityID foreign key references the Vendor. BusinessEntityID primary key. It is important that the computed column expression can not be a subquery which means you can not use SELECT statements in the expression.

You are reference a computed column in another table by using a user defined function in the expression of the calculated column. Computed columns are actually not physically created on the related database table unless they are defined as "Persisted" computed columns. You can think of computed columns as virtual columns. They are not physically stored in the related sql database table. They are calculated every time they are referenced in a sql statement.

Their values are updated when any columns that are part of their calculation change. Additionally, if a computed column references a CLR function, the Database Engine cannot verify whether the function is truly deterministic. A computed column is computed from an expression. Collectives on Stack Overflow. Learn more. Asked 2 years, 11 months ago. Active 2 years, 11 months ago. Viewed 1k times. Improve this question. Kritul Rathod Kritul Rathod 65 11 11 bronze badges.

Drop the index, add the column, recreate the the index -- it has to be rebuilt anyway. All-at-once is the best approach. HABO - Computed columns aren't stored as their original text.