MS Sql数据库常用语句

创建表

CREATE TABLE SC(
Sno CHAR(9),
Cno CHAR(9),
PRIMARY KEY(Sno,Cno),
FOREIGN KEY(Sno) REFERENCES Student(Sno),
FOREIGN KEY(Cno) REFERENCES Course(Cno)
);
create table Student(
Sno char(9) not null unique,
Sname char(20) unique,
Ssex char(2),
Sage numeric(2,0),
Sdept char(20)
)；
create table SC(
Sno char(9),
Cno char(9),
primary key (Sno,Cno),
foreign key (Sno) references Student (Sno),
foreign key (Cno) references Course (Cno)
);

删除表

DROP TABLE SC

增加列

ALTER TABLE Student
ADD Scome DATE

更改数据类型

ALTER TABLE Student
ALTER COLUMN Sage SMALLINT

Sname列添加唯一约束

ALTER TABLE Student
add CONSTRAINT sname_con UNIQUE(Sname)

删除唯一约束

ALTER TABLE Student
DROP CONSTRAINT sname_con

查看表结构

exec sp_help Student

插入数据

INSERT INTO Student
VALUES(‘001’,‘张三’,‘男’,‘18’,‘计算机系’,‘20210901’),
(‘002’,‘李四’,‘女’,‘19’,‘外语系’,‘20210901’),
(‘003’,‘王五’,‘男’,‘19’,‘计算机系’,‘20210901’);

删除表内容

DELETE FROM Student WHERE Sno=‘001’ OR Sno=‘002’

DELETE FROM SC

INSERT INTO Course
VALUES(‘001’,‘数据结构’,‘01’,‘5’)

INSERT INTO Course(Cno,Cname)
VALUES(‘002’,‘英语’)

INSERT INTO SC (Sno,Cno)
VALUES(‘001’,‘001’),
(‘002’,‘001’),
(‘003’,‘002’),
(‘001’,‘002’);

更新表内容

UPDATE Student
SET Sage=20
WHERE Sno=‘001’

UPDATE Student
SET Sage= Sage+1
WHERE Sdept=‘计算机系’

表内添加列

ALTER TABLE SC
ADD Grade

UPDATE SC
SET Grade=90
WHERE Sno='001’and cno=‘002’

查询语句

SELECT Sname, Sdept FROM Student

SELECT Sno,Cno,Grade FROM SC
SELECT DISTINCT Sno,Cno,Grade FROM SC
SELECT DISTINCT Sno,Grade FROM SC --去重复

SELECT Sname,Sage FROM Student
WHERE Sage<20;

SELECT Sname,Sage FROM Student
WHERE NOT Sage<20;

SELECT Sname,Sage FROM Student
WHERE Sage BETWEEN 19 and 21

SELECT Sname,Ssex,Sage FROM Student
WHERE Sdept IN(‘计算机系’,‘外语系’)

%匹配多个字符 _匹配一个字符

INSERT INTO Student(Sno,Sname)
VALUES (‘004’,‘张三三’)
SELECT * FROM Student
WHERE Sname LIKE ‘张%’
SELECT * FROM Student
WHERE Sname LIKE ‘张_’

查询以”DB_“开投，且倒数第三个字符为i的课程情况

INSERT INTO Course(Cno,Cname)
VALUES(‘003’,‘DB_Design’)
SELECT * FROM Course
WHERE Cname LIKE ‘DB_%i__’ ESCAPE ‘’ --’’ 表示为转意字符

针对空值或非空值进行过滤

SELECT * FROM Course
WHERE Ccredit IS NULL
SELECT * FROM Course
WHERE Ccredit IS NOT NULL

统计学生人数

SELECT COUNT(*) FROM Student
SELECT COUNT(DISTINCT(Ssex)) FROM Student

SELECT Sno,COUNT(Sno) FROM SC
GROUP BY Sno

ASC升序为缺省值 DESC 降序

SELECT * FROM Student
WHERE Sdept=‘计算机系’
ORDER BY Sage DESC

SELECT Sno,COUNT(Sno) FROM SC
GROUP BY Sno ORDER BY COUNT(*)

SELECT Sno FROM SC
GROUP BY Sno HAVING COUNT(*)>2

SELECT Sno,COUNT(Sno) FROM SC
WHERE Grade >=90
GROUP BY Sno HAVING COUNT(*)>1

SELECT Student.,Course. FROM Student,Course --很少使用，没意义

查询每个学生对应的选课情况

SELECT Student.,SC. FROM Student,SC
WHERE Student.Sno=SC.Sno

SELECT Student.Sno,Sname,Sage,Sdept,SC.Cno,Grade
FROM Student,SC
WHERE Student.Sno=SC.Sno

SELECT first.Cno,second.Cpno
FROM Course first , Course second
WHERE first.Cpno = second.Cno

SELECT * FROM Student
SELECT * FROM Course
SELECT * FROM SC