To perform a union operation:

Question

"the UNION must have the same number of columns. The columns must also have the same data types. Also, the columns in each SELECT statement must be in the same order." I suppose that essentially means the columns in queries must be the same.

Answer 1

They may have different names, but otherwise, yeah, pretty much. The columns always represent the same thing in practical cases.

Answer 2

columns in queries must be same