//选用那个数据库
USE tests;
//查看已有表格
SHOW TABLES;
//创建表格
create table table course
（
cou_id int,
cou_name varchar(20)
）
//查询语句
SELECT cou_id,cou_name FROM course;
SELECT * FROM course;
//插入语句
INSERT INTO course VALUES(4,’高数’);
INSERT INTO course(cou_id,cou_name) VALUES(5,’物理’);
//删除语句
DELETE FROM course WHERE cou_id=5;
//修改语句
UPDATE course SET cou_name=’化学’ WHERE cou_id=1;
//条件查询
SELECT cou_name FROM course WHERE cou_id=2;
//多表查询
SELECT * FROM course c,student s,xuankebiao xu
WHERE c.cou_id=xu.xuan_id AND s.stu_id=xu.id;
SELECT c.cou_name,AVG(xu.cod) FROM course c,student s,xuankebiao xu
WHERE c.cou_id=xu.xuan_id AND s.stu_id=xu.id
GROUP BY c.cou_name ;
SELECT s.stu_name,c.cou_name,xu.cod FROM course c,student s,xuankebiao xu
WHERE c.cou_id=xu.xuan_id AND s.stu_id=xu.id
AND c.cou_name=’语文’
ORDER BY xu.cod ASC;
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