How do you add a computed column to a Table?

Question

How can I add a computed column to a table that already exists? S.O. has Computed Column Help - TSQL but no information about adding them.

Chris Pfohl · Accepted Answer · 2014-01-06T15:19:05.647

120

The syntax I was looking for is:

alter table TABLE_NAME
add [column_name] as (**COLUMN-SQL**)

edited Jan 06 '14 at 15:19

answered Jun 15 '12 at 21:26

Chris Pfohl

2

`alter table TABLE_NAME add [column_name] as (**COLUMN-SQL**)` – David Knight Oct 31 '13 at 16:31
6

EX: `alter table TABLE_NAME add [double_count] as (count * 2)` – Veeresh Honnaraddi Dec 02 '15 at 05:10
27

To create a persisted column (calculated when the data is inserted) you can add the Persisted keyword: alter table TABLE_NAME add [column_name] as (COLUMN-SQL) **PERSISTED** – Sal Sep 23 '16 at 19:47
THis does now work when adding Row_Number column. ALTER TABLE MYDB.[dbo].[Table1] ADD Rn INT NOT NULL AS (ROW_NUMBER() OVER (PARTITION BY [MyColumn] ORDER BY [MyColumn])); – Data Engineer Mar 05 '19 at 17:30
2

I imagine that's a result of using a windowing function in a calculated column. – Chris Pfohl Mar 05 '19 at 17:33

1 Answers1