alter table

[FEMDEV]

Hi, Will adding a foreign key column to an existing table with data, by using alter table command affect the existing data in the table?

[Bassam Saoud]

you wont be able to create the key if any record violate that foriegn key constraint. you would probably have to clean the data [ if any violates] before being able to create the constraint

[FEMDEV]

adding a foreign key will not conflict with existing data but it would help in data integrity. am only concerned if it will result in any loss of data already existing. I know that it should not but since i've never done this before on a table in production environment with data just needed to be doubly sure that it results in no data loss.

[loyal ginger]

You may not want to do this in production environment. Try to duplicate the data in development environment and test it before doing it in a live production environment. I want to say it will not cause data loss, but I still suggest you to do it in development environment. We had mishaps on production environment before, even though we believed everything should be okay. When that happens, it may keep you in your office for a few days without any sleep.

[FEMDEV]

:) Many Thanks all. Done successfully