問題文
Two queries with different numbers of selected columns are combined with a set operator and the statement fails. Which statement about the rules for set operators is correct?
選択肢
- The select lists have to agree in the number of expressions and the database converts the matching expressions across data type groups as needed.
- The select lists have to agree in the number of expressions and the matching expressions have to carry exactly the same column names.
- The select lists have to agree in the number of expressions and the matching expressions have to belong to the same data type group.
- The select lists have to agree in the number of expressions and each query has to carry its own sort clause for the result to be ordered.