Oracle Message ORA-06504 - PL/SQL: Return types of Result Set variables or query do not match

ERRORPL/SQL: Return types of Result Set variables or query do not match
CAUSENumber and/or types of columns in a query does not match declared return type of a result set variable, or declared types of two Result Set variables do not match.
ACTIONChange the program statement or declaration. Verify what query the variable actually refers to during execution.