来自「数据库系统概论中所有的数据库例子以及课后习题和最后的上机实习的数据库。薛数据库的」· 代码 · 共 32 行

/*[例53]  查询学生姓名与教师姓名的差集
    对集合操作结果的排序
    [例53] 错误写法
     SELECT   *
        FROM    Student
        WHERE Sdept= 'CS'
        ORDER BY Sno
        UNION
        SELECT *
        FROM    Student
        WHERE Sage<=19
        ORDER BY  Sno；
正确写法
        SELECT *
        FROM Student
        WHERE Sdept= 'CS'
        UNION
        SELECT *
        FROM Student
        WHERE Sage<=19
        ORDER BY 1；


*/
     SELECT *
        FROM Student
        WHERE Sdept= 'CS'
        UNION
        SELECT *
        FROM Student
        WHERE Sage<=19
        ORDER BY 2