This blog is mainly used to show an example of MySQL practice. By practicing this example, you can achieve the effect of getting started with MySQL.
1. Requirements:
Design database table storage: (user test information)
user information, test time, test subjects and test scores, and your grade!
Test data:
U001, Zhang San, 1985-09-09, Guangzhou Tianhe,
java, 80, basic class, exam time is 2014-01-01
jsp, 90, employment class, exam time is 2014-03-01
mysql, 90 , Employment class, exam time is 2014-04-04
U002, Li Si, 1995-09-09, Guangzhou Yuexiu,
java,67, Basic class, exam time is 2014-01-01
mysql,90, Employment class, exam time For 2014-04-04
………….(Enter other records)Hint: Four tables are best (use constraints)
Query requirements:
1. Query the results of students whose student number is U001 taking the 2014-01-01 “java” course exam, and request to output the student’s name and score
2. Query the location of the students who passed the exam (higher than 60 points). Name, , the learning stage to which they belong, the name of the exam subject, and the student's grades.
Use sub-query to filter students whose birth date is older than "Li Si"
Query the list of students with a score of 60-80 in the "java" course exam
Query the highest and lowest scores in the latest "mysql" exam
Query
Requirement (stored procedure) Count and display the average score
of 2014-04-04 mysql exam Poor test scores"
The SQL statement of MySQL is as follows:
-- 创建数据库
CREATE DATABASE IF NOT EXISTS test_message CHARACTER SET utf8;
USE test_message;
DROP TABLE user_test;
-- 创建用户考试信息表
CREATE TABLE user_test(
id INT PRIMARY KEY AUTO_INCREMENT,
user_id VARCHAR(8),
test_date DATE,
course_id INT, -- 外键，考试科目的
math FLOAT(5,2), -- 考试成绩
grade_id INT
);
DROP TABLE IF EXISTS course ;
-- 考试科目表
CREATE TABLE course(
id INT PRIMARY KEY,
course_name VARCHAR(40)
);
DROP TABLE IF EXISTS grade;
-- 年级表
CREATE TABLE grade(
id INT PRIMARY KEY,
grade_name VARCHAR(5)
);
DROP TABLE IF EXISTS user_message;
-- 用户信息表
CREATE TABLE user_message(
id VARCHAR(8) PRIMARY KEY,
user_name VARCHAR(10),
user_birthday DATE,
zone VARCHAR(20)
);
-- 创建用户考试信息表和用户表的外键
ALTER TABLE user_test ADD CONSTRAINT user_test_user_message_fk FOREIGN KEY(user_id) REFERENCES user_message(id);
-- 创建用户考试信息表和年级的外键
ALTER TABLE user_test ADD CONSTRAINT user_test_grade_fk FOREIGN KEY(grade_id) REFERENCES grade(id);
-- 创建用户考试信息表和科目的外键
ALTER TABLE user_test ADD CONSTRAINT user_test_course_fk FOREIGN KEY(course_id) REFERENCES course(id);
-- 插入用户表的数据
INSERT INTO user_message
(id,
user_name,
user_birthday,
zone)
VALUES ('U001',
'张三',
'1985-09-09',
'广州天河'),
('U002',
'李四',
'1995-09-09',
'广州越秀'),
('U003',
'王五',
'1996-09-08',
'广州番禺');
-- 插入年级的数据
INSERT INTO grade
(id,
grade_name)
VALUES (1,
'基础班'),
(2,
'就业班'),
(3,
'进阶版');
-- 插入科目表的数据
INSERT INTO course(id,course_name) VALUES(1,'java'),(2,'jsp'),(3,'mysql'),(4,'ajax'),(5,'html');
-- 插入用户考试信息表的数据
INSERT INTO user_test(
user_id,
test_date,
course_id, -- 外键，考试科目的
math, -- 考试成绩
grade_id
) VALUES(
'U001',
'2014-01-01',
'1',
'80.00',
'1'),(
'U001',
'2014-03-01',
'2',
'90',
'2'),(
'U001',
'2014-04-04',
'3',
'85',
'2'),(
'U002',
'2014-01-01',
'1',
'67',
'1'),(
'U002',
'2014-04-04',
'3',
'90',
'2'),(
'U002',
'2014-05-04',
'2',
'80',
'2'),(
'U003',
'2014-06-04',
'1',
'80',
'1'),(
'U001',
'2014-01-01',
'2',
'90',
2),(
'U001',
'2014-04-04',
'3',
'96',
2);
-- 查询用户考试信息表
SELECT * FROM user_test;
DELETE FROM user_test;
-- 查询需求
-- 1. 查询学号是U001的学生参加2014-01-01 “java”课程考试的成绩，要求输出学生姓名和成绩
-- 方法一
SELECT user_name,math FROM user_test,user_message,course WHERE user_message.id=user_test.user_id
AND user_test.course_id=course.id
AND user_test.user_id='U001'
AND user_test.test_date='2014-01-01'
AND course.course_name='java';
-- 方法二
SELECT user_name,math FROM user_test INNER JOIN user_message INNER JOIN course ON user_test.user_id=user_message.id
AND user_test.course_id=course.id
AND user_test.user_id='U001'
AND user_test.test_date='2014-01-01'
AND course.course_name='java';
-- 查询出通过考试（高于80分）的学员所在的姓名、、所属学学习阶段、考试科目名称、学员的成绩。
-- 用别名
SELECT user_name,grade_name,course_name,math FROM user_test t,user_message m,course c,grade g
WHERE t.user_id=m.id
AND t.course_id=c.id
AND t.grade_id=g.id
AND t.math>80;
-- 3利用子查询语句，筛选出生日期比“李四”大的学生
SELECT user_name FROM user_message WHERE user_birthday>(SELECT user_birthday FROM user_message WHERE user_name='李四');
SELECT * FROM user_message;
-- 4查询“java”课程考试成绩为60-80分的学生名单
SELECT user_name FROM user_test t,user_message m,course c WHERE t.course_id=c.id
AND t.user_id=m.id
AND c.course_name='java'
AND t.math>=60
AND t.math<80;
-- 5查询参加最近一次“mysql”考试成绩最高分和最低分
SELECT MAX(math),MIN(math) FROM user_test t INNER JOIN course c ON t.course_id=c.id
AND c.course_name='mysql'
AND test_date=(SELECT MAX(test_date) FROM user_test t INNER JOIN course c ON t.course_id=c.id
AND c.course_name='mysql')
ORDER BY math DESC;
-- 6.查询出基础班考试的平均成绩；
SELECT AVG(math) FROM user_test t INNER JOIN grade g ON t.grade_id=g.id
AND g.grade_name='基础班';
-- 分组查询
SELECT grade_name,AVG(math) FROM user_test t,grade g WHERE t.grade_id=g.id GROUP BY g.grade_name;
-- 7需求（存储过程）
-- 7.1统计并显示2014-04-04的mysql考试平均分
-- 7.2如果平均分在70以上，显示“考试成绩优秀”
-- 7.3 如果在70以下，显示“考试成绩较差”
-- 删除存储过程
DROP PROCEDURE pro_test;
-- 创建存储过程
DELIMITER $
CREATE PROCEDURE pro_test(OUT avg_math DOUBLE,OUT str VARCHAR(6))
BEGIN
SELECT AVG(math) INTO avg_math FROM user_test t,course c WHERE t.course_id=c.id
AND t.test_date='2014-04-04'
AND c.course_name='mysql';
IF avg_math>=70 THEN
SET str='考试成绩优秀';
ELSE
SET str='考试成绩较差';
END IF;
END $
-- 执行存储过程
CALL pro_test(@avg_math,@str);
SELECT @avg_math,@str;