Seaquel
SQL Server error code

SQL Server error 205

SQL Server raises error 205 at severity 16, which marks a problem with the query or data that you can correct.

All queries combined using a UNION, INTERSECT or EXCEPT operator must have an equal number of expressions in their target lists.
Msg205
Severity16
Group0–999

How to fix it

In other databases

Source: Database Engine events and errors