Change datatype from varchar to bigint not working

Hello,

I would like to change the datatype on a particular column from varchar to bigint across 100's of tables within a database.

I have the command ready which is:

ALTER TABLE tablename ALTER COLUMN columnname BIGINT

The problem happening is that it seems there are constraints across all the columns in every tables.

The error message is:

Server: Msg 5074, Level 16, State 1, Line 1
The object 'DF__tablename__columnname__0ABD916C' is dependent on column 'columnname'.
Server: Msg 4922, Level 16, State 1, Line 1
ALTER TABLE ALTER COLUMN columnname failed because one or more objects access this column.

I understand that if I delete this constraint, then it will let me modify the datatype of the column, but since there are tons of them and they are randomly named, how do I achive changing the datatype across multiple tables in bulk.Hi

This should help you:
http://www.sqlteam.com/article/default-constraint-names