How to add a default value to an already existing column?
Use:
ALTER TABLE dbo.mytableADD CONSTRAINT def_mycolumn DEFAULT GETDATE() FOR mycolumnFor more info, see: Working with Default Constraints
If you want to change the default value of an already existing column. You need to first drop the constraint and then add the constraint all over again as below
ALTER TABLE <TABLE> DROP CONSTRAINT <CONSTRAINT NAME>ALTER TABLE <TABLE> ADD CONSTRAINT <CONSTRAINT NAME> DEFAULT <VALUE> for <COLUMN>If you are not having the Constraint details of the table, you can use the below query
sp_helpconstraint <TABLE>