Yes/No columns in logical database design I have an assignment where I have to design a logical model. 

I have a relation NURSE that has "nurse_id" and "certification". The certification attribute has yes/no values, so, should I move it to another relation, or is it okay to keep it in the same NURSE relation?

And is the suitable data type for that attribute (CHAR)?

Thank you,
For a logical database design you don’t need to specify TINYINT or CHAR — that’s a physical consideration. Some DBMSes such as Postgres have a BOOLEAN data-type which would be preferred, but again, a physical design.

In your logical model you could assume a binary-valued datatype with Yes and No as the two values (or a ternary-valued type if NULL should also be allowed).

You have two questions actually; for the other, yes, I would keep the flag in the same relation.