MySQL数据库的使用方法(连表查询、分页查询)

数据库连表查询

学生表student

老师表teacher

课程表course

选课表student_course

1 按“0001”号课程成绩由高到低顺序显示所有学生学号、姓名、成绩（二表连接）；

SELECT
       student.student_id,
       student.student_name,
       student_course.score
FROM
       student,
       student_course
WHERE
       student.student_id = student_course.student_id
AND student_course.course_id = '0001'
ORDER BY
       student_course.score DESC; #DESC代表降序排列;ASC代表升序排列

当两个（多个）表中有相同的字段（属性，列名）时，使用表名（或表别名）.列名的形式对查询内容和条件内容进行区分。

运行结果：

2 按“高等数学”课程成绩由高到低顺序显示所有学生姓名、学号、分数、课程名（三表连接）；

SELECT
       st.student_id,
       st.student_name,
       sc.score,
       co.course_name
FROM
       student AS st,
       student_course AS sc,
       course AS co
WHERE
       st.student_id = sc.student_id
AND sc.course_id = co.course_id
AND co.course_name = '高等数学'
ORDER BY
       sc.score DESC; #DESC代表降序排列;ASC代表升序排列

运行结果：

3 查询有薪水差额的任意两位教师（单表连接查询）；

SELECT
       t1.teacher_id AS '教工号1',
       t1.teacher_name AS '教师姓名1',
       t2.teacher_id AS '教工号2',
       t2.teacher_name AS '教师姓名2'
FROM
       teacher t1,
       teacher t2
WHERE
       t1.teacher_salary > t2.teacher_salary;

运行结果：

4 查询既学过“0001”又学过“0002”号课程的所有学生学号；

SELECT
	sc1.student_id '学号'
FROM
	student_course sc1,
	student_course sc2
WHERE
	sc1.student_id = sc2.student_id
AND sc1.course_id = '0001'
AND sc2.course_id = '0002';

运行结果：

5 查询“0001”号课程比“0002”号课程成绩低的所有学生学号姓名；

SELECT
	st.student_id '学号',
	st.student_name '姓名'
FROM
	student_course sc1,
	student_course sc2,
	student st
WHERE
	sc1.student_id = sc2.student_id
AND sc1.student_id = st.student_id
AND sc1.course_id = '0001'
AND sc2.course_id = '0002'
AND sc1.score < sc2.score;

运行结果：

6. 查询“0003”老师教的所有的学生

SELECT
	st.*
FROM
        student as st inner join teacher as th on st.teacher_id=th.teacher_id where th.teacher_id =0003

mysql数据库分页查询

select * from student limit 2,3

运行结果

上面查询中的2代表从第2条数据之后开始，注意是第2条数据之后，不包含第2条数据。3代表总共查询3条记录。那么limit 2,3代表从第2条(不包含第2条) 数据开始查询出3条记录。

创建表及插入数据

我们按照以下的语句对我们的数据库操进行建表和插入数据，方便接下来对我们的两张表进行操作和演示

#数据库建表
CREATE TABLE IF NOT EXISTS 'student' (
    'id' INT AUTO_INCREMENT,
    'name' VARCHAR(18) NOT NULL COMMENT '姓名',
    'age' VARCHAR(18) NOT NULL COMMENT '年龄',
    'weight' VARCHAR(18) NOT NULL COMMENT '体重',
    'sex' VARCHAR(18) NOT NULL COMMENT '性别',
    'height' VARCHAR(18) NOT NULL COMMENT '身高',
    'teacher_id' INT NOT NULL COMMENT '教师id',
    'create_time' datetime NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '创建时间',
    PRIMARY KEY ('id')
) ENGINE = InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE IF NOT EXISTS 'teacher'(
    'id' INT AUTO_INCREMENT,
    'name' VARCHAR(18) NOT NULL COMMENT '姓名',
    'age'  VARCHAR(18) NOT NULL COMMENT '年龄',
    'weight'  VARCHAR(18) NOT NULL COMMENT '体重',
    'height' VARCHAR(18) NOT NULL COMMENT '身高',
    'sex'  VARCHAR(18) NOT NULL COMMENT '性别',
    'create_time' datetime NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '创建时间',
    PRIMARY KEY ('id')
)ENGINE = InnoDB DEFAULT CHARSET=utf8;
# 在学生表中插入数据
INSERT INTO student(name,age,weight,sex,height,teacher_id)VALUES
                    ("花花","18","50","女","165",1),
                    ("菲菲","17","47","男","162",1),
                    ("西西","19","45","女","161",2),
                    ("玥玥","16","40","女","160",1),
                    ("涵涵","15","49","男","164",2),
                    ("涵涵","17","48","男","163",2),
                    ("若若","20","45","女","161",1);
# 在老师表中插入数据
INSERT INTO teacher (name,age,weight,height,sex)VALUES
                    ("高飞","26","64","170","女"),
                    ("张宇","28","74","179","男");