Advantage Error Guide
Problem: Each resulting column of the individual queries in the UNION statement must be the same data type for all queries. For example, "SELECT lastname FROM table1 UNION SELECT DOB FROM table2" is not valid because the second SELECT returns a column with data type of date while the first SELECT returns only a column of characters.
Solution: Adjust the SELECT clauses in the UNION statement so they all return the same data type at each column position.