1.(单选题)Oracle数据库中,在SQL语句中连接字符串的方法是:(). A)CAT B)CONCAT C)JOIN D)UNION 2.(单选题)在数据库中,有一个名为seq的序列对象,以下语句能返回下一个序列值的是: A)select seq.ROWNUM from dual; B)select seq.ROWID from dual; C)select seq.CURRVAL from dual; D)select seq.NEXTVAL from dual; 3.(单选题)selec…