【0031】SQL查询--简单查询--投影运算

1、查询指定列

SELECT classNo,className,instituteFROM class

2、消除重复组

SELECT DISTINCT instituteFROM class

3、查询所有列

SELECT *FROM class

4、给属性列取名

SELECT institute 所属学院,classNo 班级编号,className 班级名称FROM class

SELECT institute AS 所属学院,classNo AS 班级编号,className AS 班级名称FROM class

5、查询经过计算的列

SELECT courseNo 课程号,LOWER(courseName) 课程名,courseHour/16 AS 周课时FROM Course