SQL 数据库操作练习：学生选课信息管理

(1) 建立 SC 表的 SQL 语句：

CREATE TABLE SC (
  Sno CHAR(10) NOT NULL,
  Cno CHAR(10) NOT NULL,
  Grade DECIMAL(4,1) NOT NULL,
  PRIMARY KEY (Sno, Cno),
  FOREIGN KEY (Sno) REFERENCES Student(Sno) ON DELETE CASCADE,
  FOREIGN KEY (Cno) REFERENCES Course(Cno) ON DELETE CASCADE,
  CHECK (Grade >= 0 AND Grade <= 100)
);

(2) 查询年龄大于 19 岁的'计算机系'的学生学号和姓名的 SQL 语句：

SELECT Sno, Sname
FROM Student
WHERE Sdept = '计算机系' AND Sage > 19;

(3) 将所有女生的成绩加上 10 分的 SQL 语句：

UPDATE SC
SET Grade = Grade + 10
WHERE Sno IN (
  SELECT Sno
  FROM Student
  WHERE Ssex = '女'
);

(4) 建立视图 E_W 的 SQL 语句：

CREATE VIEW E_W AS
SELECT Sno, Sname, Cno, Grade
FROM SC
WHERE Sno IN (
  SELECT Sno
  FROM Student
  WHERE Sdept = '计算机系'
);