What Is Union Compatible?

UNION-compatible means that you must align numbers with numbers, strings with strings, and date times with date times. In this example, the column in the result set called "rowvalue2" will have string values, hence it is necessary to CAST the numeric count as VARCHAR.

Two relations are Union compatible if,
1. Two relations have the same degree(degree is the no of attributes a relation has got)
2. Domains of attributes are same