数据库操作-6(其他)

1、SQL索引的建立:

CREATE INDEX age_index
ON Student_2(age)

DROP INDEX age_index on Student_2;

--
SELECT sno,sname 
FROM Student_2
WHERE age=19;

2、创建视图

CREATE VIEW D_student 
AS 
SELECT sno, sname, age FROM Student
WHERE dept = 'CS'

3、删除视图

DROP VIEW D_student 

4、SQL编程

-- case
select sno as '学号', cno as '课程号',
	CASE 
		WHEN grade>=90 THEN 'A'
		WHEN grade>=80 THEN 'B'
		WHEN grade>=70 THEN 'C'
		WHEN grade>=60 THEN 'D'
		WHEN grade<60 THEN 'E'
	END AS '成绩'
FROM SC2
ORDER BY sno