Either OR non-null constraints in MySQL

Question

What\'s the best way to create a non-NULL constraint in MySQL such that fieldA and fieldB can\'t both be NULL. I don\'t care if either one is NULL by itself, just as long as the

Answer 1

I've done something similar in SQL Server, I'm not sure if it will work directly in MySQL, but:

ALTER TABLE tableName ADD CONSTRAINT constraintName CHECK ( (fieldA IS NOT NULL) OR (fieldB IS NOT NULL) );

At least I believe that's the syntax.

However, keep in mind that you cannot create check constraints across tables, you can only check the columns within one table.