CODEWITHSUNDEEP
sqlsql-server
Teeko
Teeko

Reputation: 53

SQL How to update a column with data from the same table

ID START_DATE     ADD_DAYS    NEW_DATE    
------------------------------------------
1  02/02/2017     5     
2  06/24/2017     3      
3  07/14/2017     9      
4  05/19/2017     12

I have the following table and I want to go in and update the column NEW_DATE with data that I read from the table itself. I am struggling to understand the correct MS SQL to achieve that. Any help?

Upvotes: 1

Views: 63

Answers (2)

eugenioy
eugenioy

Reputation: 12383

UPDATE MYTABLE SET NEW_DATE = DATEADD(day, ADD_DAYS, START_DATE)

If you need to update rows using conditions, you can do for example:

UPDATE MYTABLE SET NEW_DATE = DATEADD(day, ADD_DAYS, START_DATE)
WHERE ID < 10

Upvotes: 3

Icarus
Icarus

Reputation: 63956

If you can control the schema, it might be worth adding this NEW_DATE column as a calculated column. 

ALTER TABLE table_name ADD NEW_DATE as DATEADD(DAY,ADD_DAYS,START_DATE)

That way you don't need to update anything and any changes to add_days or start_date are automatically recalculated

Upvotes: 0

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