sql语句练习50题

00 相关参考资料

01 表和测试数据

CREATE TABLE `course`  (
  `c_id` varchar(20) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  `c_name` varchar(20) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL DEFAULT '',
  `t_id` varchar(20) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  PRIMARY KEY (`c_id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci COMMENT = '课程表' ROW_FORMAT = Dynamic;

INSERT INTO `course` VALUES ('01', '语文', '02');
INSERT INTO `course` VALUES ('02', '数学', '01');
INSERT INTO `course` VALUES ('03', '英语', '03');
INSERT INTO `course` VALUES ('04', '化学', '01');

CREATE TABLE `score`  (
  `s_id` varchar(20) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  `c_id` varchar(20) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  `s_score` int(3) NULL DEFAULT NULL,
  PRIMARY KEY (`s_id`, `c_id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci COMMENT = '成绩表' ROW_FORMAT = Dynamic;

INSERT INTO `score` VALUES ('01', '01', 80);
INSERT INTO `score` VALUES ('01', '02', 56);
INSERT INTO `score` VALUES ('01', '03', 99);
INSERT INTO `score` VALUES ('01', '04', 80);
INSERT INTO `score` VALUES ('02', '01', 70);
INSERT INTO `score` VALUES ('02', '02', 59);
INSERT INTO `score` VALUES ('02', '03', 80);
INSERT INTO `score` VALUES ('03', '01', 80);
INSERT INTO `score` VALUES ('03', '02', 80);
INSERT INTO `score` VALUES ('03', '03', 80);
INSERT INTO `score` VALUES ('04', '01', 50);
INSERT INTO `score` VALUES ('04', '02', 80);
INSERT INTO `score` VALUES ('04', '03', 20);
INSERT INTO `score` VALUES ('05', '02', 80);
INSERT INTO `score` VALUES ('05', '03', 87);
INSERT INTO `score` VALUES ('06', '02', 58);
INSERT INTO `score` VALUES ('06', '04', 99);
INSERT INTO `score` VALUES ('07', '01', 58);
INSERT INTO `score` VALUES ('07', '03', 98);

CREATE TABLE `student`  (
  `s_id` varchar(20) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  `s_name` varchar(20) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL DEFAULT '',
  `s_birth` varchar(20) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL DEFAULT '',
  `s_sex` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL DEFAULT '',
  PRIMARY KEY (`s_id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci COMMENT = '学生表' ROW_FORMAT = Dynamic;

INSERT INTO `student` VALUES ('01', '赵雷', '1990-01-01', '男');
INSERT INTO `student` VALUES ('02', '郑竹', '1990-12-21', '男');
INSERT INTO `student` VALUES ('03', '孙风', '2000-04-12', '男');
INSERT INTO `student` VALUES ('04', '李云', '2002-04-16', '男');
INSERT INTO `student` VALUES ('05', '周梅', '2003-04-17', '女');
INSERT INTO `student` VALUES ('06', '吴兰', '2008-04-11', '女');
INSERT INTO `student` VALUES ('07', '郑竹', '1989-05-01', '女');
INSERT INTO `student` VALUES ('08', '王菊', '1990-01-20', '女');
INSERT INTO `student` VALUES ('09', '王菊', '1998-01-20', '女');

CREATE TABLE `teacher`  (
  `t_id` varchar(20) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  `t_name` varchar(20) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL DEFAULT '',
  PRIMARY KEY (`t_id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci COMMENT = '教师表' ROW_FORMAT = Dynamic;

INSERT INTO `teacher` VALUES ('01', '张三');
INSERT INTO `teacher` VALUES ('02', '李四');
INSERT INTO `teacher` VALUES ('03', '王五');
INSERT INTO `teacher` VALUES ('04', '李师师');

02 试题

1、查询"01"课程比"02"课程成绩高的学生的信息及课程分数

-- 1、查询"01"课程比"02"课程成绩高的学生的信息及课程分数(03版)
SELECT
    a.*,
    b.s_score AS '01',
    c.s_score AS '02' 
FROM
    student a,
    score b,
    score c 
WHERE
    a.s_id = b.s_id 
    AND a.s_id = c.s_id 
    AND b.c_id = '01' 
    AND c.c_id = '02' 
    AND b.s_score > c.s_score;

-- 1、查询"01"课程比"02"课程成绩高的学生的信息及课程分数(02版)
SELECT
    a.*,
    b.s_score AS '01',
    c.s_score AS '02' 
FROM
    student a
    INNER JOIN score b ON a.s_id = b.s_id 
    AND b.c_id = '01'
    INNER JOIN score c ON b.s_id = c.s_id 
    AND c.c_id = '02' 
WHERE
    b.s_score > c.s_score;

-- 1、查询"01"课程比"02"课程成绩高的学生的信息及课程分数(01版)
SELECT
    a.*,
    b.s_score AS '01',
    c.s_score AS '02' 
FROM
    student a
    INNER JOIN ( SELECT s_id, s_score FROM score WHERE c_id = '01' ) b ON a.s_id = b.s_id
    INNER JOIN ( SELECT s_id, s_score FROM score WHERE c_id = '02' ) c ON b.s_id = c.s_id 
WHERE
    b.s_score > c.s_score;

2、查询平均成绩大于60分的学生的学号和平均成绩

-- 2、查询平均成绩大于60分的学生的学号和平均成绩
SELECT
    s_id,
    round( avg( s_score ), 2 ) AS avg_score 
FROM
    score 
GROUP BY
    s_id 
HAVING
    avg_score > 60;

ROUND() 函数

在mysql中，round函数用于数据的四舍五入，它有两种形式：

1、round(x,d) ，x指要处理的数，d是指保留几位小数

3、查询所有同学的学生编号、学生姓名、选课总数、所有课程的总成绩

注意是所有同学

-- 3、查询所有同学的学生编号、学生姓名、选课总数、所有课程的总成绩
SELECT
    a.s_id AS '编号',
    a.s_name AS '姓名',
    count( b.s_id ) AS '选课总数',
    IFNULL( sum( b.s_score ), 0 ) AS '总成绩' 
FROM
    student a
    LEFT JOIN score b ON a.s_id = b.s_id 
GROUP BY
    a.s_id;

IFNULL() 函数

IFNULL() 函数用于判断第一个表达式是否为 NULL，如果为 NULL 则返回第二个参数的值，如果不为 NULL 则返回第一个参数的值。

IFNULL() 函数语法格式为：

IFNULL(expression, alt_value)

4、查询"李"姓老师的数量

-- 4、查询"李"姓老师的数量 
SELECT
    count(*) 
FROM
    teacher 
WHERE
    t_name LIKE '李%';

5、查询学过"张三"老师授课的同学的信息

-- 5、查询学过"张三"老师授课的同学的信息 
SELECT
    d.* 
FROM
    teacher a
    INNER JOIN course b ON a.t_id = b.t_id 
    AND a.t_name = '张三'
    INNER JOIN score c ON b.c_id = c.c_id
    INNER JOIN student d ON c.s_id = d.s_id GROUP BY d.s_id

6、查询没学过"张三"老师授课的同学的信息

-- 6、查询没学过"张三"老师授课的同学的信息 
SELECT
    * 
FROM
    student 
WHERE
    s_id NOT IN (
    SELECT DISTINCT
        d.s_id 
    FROM
        teacher a
        INNER JOIN course b ON a.t_id = b.t_id 
        AND a.t_name = '张三'
        INNER JOIN score c ON b.c_id = c.c_id
    INNER JOIN student d ON c.s_id = d.s_id)

7、查询学过编号为"01"并且也学过编号为"02"的课程的同学的信息

求交集一般用inner join

-- 7、查询学过编号为"01"并且也学过编号为"02"的课程的同学的信息
SELECT
    c.* 
FROM
    ( SELECT * FROM score WHERE c_id = '01' ) a
    INNER JOIN score b ON a.s_id = b.s_id 
    AND b.c_id = '02'
    INNER JOIN student c ON a.s_id = c.s_id;

SELECT
    * 
FROM
    student 
WHERE
    s_id IN ( SELECT s_id FROM score WHERE c_id = '01' ) 
    AND s_id IN ( SELECT s_id FROM score WHERE c_id = '02' );

8、查询学过编号为"01"但是没有学过编号为"02"的课程的同学的信息

-- 8、查询学过编号为"01"但是没有学过编号为"02"的课程的同学的信息
SELECT
    c.* 
FROM
    ( SELECT * FROM score WHERE c_id = '01' ) a
    INNER JOIN student c ON a.s_id = c.s_id 
WHERE
    c.s_id NOT IN ( SELECT s_id FROM score WHERE c_id = '02' );

SELECT
    * 
FROM
    student 
WHERE
    s_id IN ( SELECT s_id FROM score WHERE c_id = '01' ) 
    AND s_id NOT IN ( SELECT s_id FROM score WHERE c_id = '02' );

9、查询学全所有课程的同学的信息

统计函数不分组也能用,统计函数后不要留空格

-- 9、查询学全所有课程的同学的信息 
select a.* from student a inner join (select s_id,count(c_id)as num from score group by s_id having num=(select count(*) from course ))b on a.s_id=b.s_id

-- 9、查询学全所有课程的同学的信息
SELECT * FROM student WHERE s_id IN ( SELECT s_id FROM score GROUP BY s_id HAVING count( c_id )=( SELECT count(*) FROM course ))

10、查询至少有一门课与学号为"07"的同学所学相同的同学的信息

-- 10、查询至少有一门课与学号为"07"的同学所学相同的同学的信息 
select * from student where s_id in(select distinct s_id from score where c_id in(select c_id from score where s_id='07') and s_id!='07')

11、查询和"07"号的同学学习的课程完全相同的其他同学的信息

-- 11、查询和"01"号的同学学习的课程完全相同的其他同学的信息 
-- 1>查询07同学没有学过的课程
select c_id from course where c_id not in ( SELECT c_id FROM score WHERE s_id = '07' );
-- 2>找出学过07同学没有学过的课程的同学
select distinct s_id from score where c_id in (select c_id from course where c_id not in ( SELECT c_id FROM score WHERE s_id = '07' ));
-- 3> 排除第二步的同学并且剩下同学学的课程数和07相同,就是最终结果
select * from student where s_id in (select s_id from score where s_id not in (select distinct s_id from score where c_id in (select c_id from course where c_id not in ( SELECT c_id FROM score WHERE s_id = '07' ))) and s_id!='07' group by s_id having count(c_id)=(select count(*) from score where s_id = '07' ));

优解

-- 11、查询和"01"号的同学学习的课程完全相同的其他同学的信息 
select * from student where s_id  in ( select s_id from score where s_id!='07' group by s_id having group_concat(c_id order by c_id) = (select group_concat(c_id order by c_id) from score where s_id='07' group by s_id) );

group_concat()函数

1、功能：将group by产生的同一个分组中的值连接起来，返回一个字符串结果。

2、语法：group_concat( [distinct] 要连接的字段 [order by 排序字段 asc/desc ] [separator '分隔符'] )

说明：通过使用distinct可以排除重复值；如果希望对结果中的值进行排序，可以使用order by子句；separator是一个字符串值，缺省为一个逗号。

注意:必须在group by后使用,效果将分组后的指定字段拼接成字符串,连接符默认为逗号

12、查询没学过"张三"老师讲授的任一门课程的学生姓名

-- 12、查询没学过"张三"老师讲授的任一门课程的学生姓名 
select s_name from student where s_id not in( select distinct s_id from score where c_id in( select b.c_id  from teacher a inner join course b on a.t_id=b.t_id and a.t_name='张三') group by s_id);

13、查询两门及其以上不及格课程的同学的学号，姓名及其平均成绩

-- 13、查询两门及其以上不及格课程的同学的学号，姓名及其平均成绩 
select a.s_id,b.s_name,a.avg_score from (select s_id,round(avg(s_score),2)as avg_score from score where s_score<60 group by s_id having count(c_id)>=2) a inner join student b on a.s_id=b.s_id;

14、按平均成绩从高到低显示所有学生的所有课程的成绩以及平均成绩

-- 14、按平均成绩从高到低显示所有学生的所有课程的成绩以及平均成绩
SELECT
    a.s_name,
    b.* 
FROM
    student a
    LEFT JOIN (
    SELECT
        s_id,
        max( CASE WHEN c_id = '01' THEN s_score ELSE NULL END ) AS '01',
        max( CASE WHEN c_id = '02' THEN s_score ELSE NULL END ) AS '02',
        max( CASE WHEN c_id = '03' THEN s_score ELSE NULL END ) AS '03',
        max( CASE WHEN c_id = '04' THEN s_score ELSE NULL END ) AS '04',
        round ( avg( s_score ), 2 ) AS avg_score 
    FROM
        score 
    GROUP BY
        s_id 
    ) b ON a.s_id = b.s_id 
ORDER BY
    b.avg_score DESC

15.查询各科成绩最高分、最低分和平均分

查询各科成绩最高分、最低分和平均分：以如下形式显示：课程ID，课程name，最高分，最低分，平均分，及格率，中等率，优良率，优秀率,及格为>=60，中等为：70-80，优良为：80-90，优秀为：>=90

SELECT
    a.c_id '课程ID',
    c_name '课程name',
    max( s_score ) '最高分',
    min( s_score ) '最低分',
    round( avg( s_score ), 2 ) '平均分',
    concat( round( sum( CASE WHEN s_score >= 60 THEN 1 ELSE 0 END )/ count( 1 )* 100, 2 ), '%' ) '及格率',
    concat(
        round( sum( CASE WHEN s_score >= 70 AND s_score < 80 THEN 1 ELSE 0 END )/ count( 1 )* 100, 2 ),
        '%' 
    ) '中等率',
    concat(
        round( sum( CASE WHEN s_score >= 80 AND s_score < 90 THEN 1 ELSE 0 END )/ count( 1 )* 100, 2 ),
        '%' 
    ) '优良率',
    concat( round( sum( CASE WHEN s_score >= 90 THEN 1 ELSE 0 END )/ count( 1 )* 100, 2 ), '%' ) '优秀率' 
FROM
    score a
    INNER JOIN course b ON a.c_id = b.c_id 
GROUP BY
    a.c_id,
    b.c_name;

注意:关联查询时,多表共有的字段返回时需要指定表,如c_id为score和course共有的字段,返回时指定a.c_id

16、按各科成绩进行排序，并显示排名(`未练习`)

-- 16、按各科成绩进行排序，并显示排名
select a.s_id,a.c_id,
        @i:=@i +1 as i保留排名,
        @k:=(case when @score=a.s_score then @k else @i end) as rank不保留排名,
        @score:=a.s_score as score
    from (
        select s_id,c_id,s_score from score GROUP BY s_id,c_id,s_score ORDER BY s_score DESC
)a,(select @k:=0,@i:=0,@score:=0)s;

17、查询学生的总成绩并进行排名(`未练习`)

-- 17、查询学生的总成绩并进行排名
select a.s_id,
    @i:=@i+1 as i,
    @k:=(case when @score=a.sum_score then @k else @i end) as rank,
    @score:=a.sum_score as score
from (select s_id,SUM(s_score) as sum_score from score GROUP BY s_id ORDER BY sum_score DESC)a,
    (select @k:=0,@i:=0,@score:=0)s;

18、查询不同老师所教不同课程平均分从高到低显示

-- 21、查询不同老师所教不同课程平均分从高到低显示 
SELECT
    a.t_id,
    t_name,
    c.c_id,
    c_name,
    round ( avg( s_score ), 2 ) avg_score 
FROM
    teacher a
    LEFT JOIN course b ON a.t_id = b.t_id
    LEFT JOIN score c ON b.c_id = c.c_id 
GROUP BY
    c.c_id,
    a.t_id 
ORDER BY
    avg_score DESC;

19、查询所有课程的成绩第2名到第3名的学生信息及该课程成绩(`未练习`)

-- 19、查询所有课程的成绩第2名到第3名的学生信息及该课程成绩
            select d.*,c.排名,c.s_score,c.c_id from (
                select a.s_id,a.s_score,a.c_id,@i:=@i+1 as 排名 from score a,(select @i:=0)s where a.c_id='01'  
                                ORDER BY a.s_score DESC  
            )c
            left join student d on c.s_id=d.s_id
            where 排名 BETWEEN 2 AND 3
            UNION
            select d.*,c.排名,c.s_score,c.c_id from (
                select a.s_id,a.s_score,a.c_id,@j:=@j+1 as 排名 from score a,(select @j:=0)s where a.c_id='02'  
                                ORDER BY a.s_score DESC
            )c
            left join student d on c.s_id=d.s_id
            where 排名 BETWEEN 2 AND 3
            UNION
            select d.*,c.排名,c.s_score,c.c_id from (
                select a.s_id,a.s_score,a.c_id,@k:=@k+1 as 排名 from score a,(select @k:=0)s where a.c_id='03' 
                                ORDER BY a.s_score DESC
            )c
            left join student d on c.s_id=d.s_id
            where 排名 BETWEEN 2 AND 3;

20、统计各科成绩各分数段人数

-- 20、统计各科成绩各分数段人数：课程编号,课程名称,[100-85],(85-70],(70-60],(0-60]及所占百分比
SELECT
    c_id '课程编号',
    c_name '课程名称',
    c1 '[100-85]',
    c2 '(85-70]',
    c3 '(70-60]',
    c4 '(0-60]',
    round( c1 / num, 2 ) '[100-85]百分比',
    round( c2 / num, 2 ) '(85-70]百分比',
    round( c3 / num, 2 ) '(70-60]百分比',
    round( c4 / num, 2 ) '(0-60]百分比',
    num '报考人数' 
FROM
    (
    SELECT
        a.c_id,
        b.c_name,
        count( 1 ) num,
        sum( CASE WHEN s_score >= 85 AND s_score <= 100 THEN 1 ELSE 0 END ) c1,
        sum( CASE WHEN s_score >= 70 AND s_score < 85 THEN 1 ELSE 0 END ) c2,
        sum( CASE WHEN s_score >= 60 AND s_score < 70 THEN 1 ELSE 0 END ) c3,
        sum( CASE WHEN s_score >= 0 AND s_score < 60 THEN 1 ELSE 0 END ) c4 
    FROM
        score a
        INNER JOIN course b ON a.c_id = b.c_id 
    GROUP BY
    a.c_id 
    ) c;

21、查询学生平均成绩及其名次(`未练习`)

select a.s_id,
                @i:=@i+1 as '不保留空缺排名',
                @k:=(case when @avg_score=a.avg_s then @k else @i end) as '保留空缺排名',
                @avg_score:=avg_s as '平均分'
        from (select s_id,ROUND(AVG(s_score),2) as avg_s from score GROUP BY s_id ORDER BY avg_s DESC)a,(select @avg_score:=0,@i:=0,@k:=0)b;

22、查询各科成绩前三名的记录(`未练习`)

-- 22、查询各科成绩前三名的记录
SELECT
    a.s_id,
    a.c_id,
    a.s_score 
FROM
    score a
    LEFT JOIN score b ON a.c_id = b.c_id 
    AND a.s_score < b.s_score 
GROUP BY
    a.s_id,
    a.c_id,
    a.s_score 
HAVING
    COUNT( b.s_id )< 3 
ORDER BY
    a.c_id,
    a.s_score DESC

23、查询每门课程被选修的学生数

-- 23、查询每门课程被选修的学生数 
SELECT
    a.c_id,
    a.c_name,
    count( 1 ) 
FROM
    course a
    INNER JOIN score b ON a.c_id = b.c_id 
GROUP BY
    a.c_id;

24、查询出只有两门课程的全部学生的学号和姓名

-- 24、查询出只有两门课程的全部学生的学号和姓名
SELECT
    b.s_id,
    b.s_name 
FROM
    score a
    INNER JOIN student b ON a.s_id = b.s_id 
GROUP BY
    a.s_id 
HAVING
    count( 1 )= 2;

25、查询男生、女生人数查询男生、女生人数

--  25、查询男生、女生人数
SELECT
    s_sex,
    count( 1 ) 
FROM
    student 
GROUP BY
    s_sex;

26、查询名字中含有"风"字的学生信息

-- 26、查询名字中含有"风"字的学生信息
SELECT
    * 
FROM
    student 
WHERE
    s_name LIKE '%风%';

27、查询同名同性学生名单，并统计同名人数

-- 27、查询同名同性学生名单，并统计同名人数
SELECT
    s_sex,
    s_name,
    count( 1 ) '同名人数' 
FROM
    student 
GROUP BY
    s_sex,
    s_name 
HAVING
    count( 1 )> 1;

28、查询1990年出生的学生名单

-- 28、查询1990年出生的学生名单
SELECT
    * 
FROM
    student 
WHERE
    s_birth LIKE '1990%'

29、查询每门课程的平均成绩，结果按平均成绩降序排列，平均成绩相同时，按课程编号升序排列

-- 29、查询每门课程的平均成绩，结果按平均成绩降序排列，平均成绩相同时，按课程编号升序排列
SELECT
    c_id,
    avg( s_score ) avg_score 
FROM
    score 
GROUP BY
    c_id 
ORDER BY
    avg_score DESC,
    c_id ASC;

30、查询平均成绩大于等于80的所有学生的学号、姓名和平均成绩

-- 30、查询平均成绩大于等于80的所有学生的学号、姓名和平均成绩
SELECT
    b.s_id,
    b.s_name,
    round( avg( s_score ), 2 ) avg_score 
FROM
    score a
    INNER JOIN student b ON a.s_id = b.s_id 
GROUP BY
    b.s_id 
HAVING
    avg_score >= 80;

31、查询所有学生的课程及分数情况；

-- 31、查询所有学生的课程及分数情况； 
SELECT
    b.s_id,
    a.s_name,
    max( CASE WHEN c_id = '01' THEN s_score ELSE NULL END ) '语文',
    max( CASE WHEN c_id = '02' THEN s_score ELSE NULL END ) '数学',
    max( CASE WHEN c_id = '03' THEN s_score ELSE NULL END ) '英语',
    max( CASE WHEN c_id = '04' THEN s_score ELSE NULL END ) '化学' 
FROM
    student a
    INNER JOIN score b ON a.s_id = b.s_id 
GROUP BY
    b.s_id;

32、查询任何一门课程成绩在70分以上的姓名、课程名称和分数；

-- 32、查询任何一门课程成绩在70分以上的姓名、课程名称和分数；
SELECT
    c.s_name,
    a.c_name,
    b.s_score,
    FRO course a
    INNER JOIN score b ON a.c_id = b.c_id 
    AND s_score >= 70
    INNER JOIN student c ON b.s_id = c.s_id;

33、查询不及格的课程(略)

34、查询课程编号为01且课程成绩在80分以上的学生的学号和姓名；

-- 34、查询课程编号为01且课程成绩在80分以上的学生的学号和姓名；
SELECT
    a.s_id,
    b.s_name 
FROM
    score a
    INNER JOIN student b ON a.s_id = b.s_id 
    AND a.c_id = '01' 
    AND a.s_score >= 80;

35、求每门课程的学生人数

-- 35、求每门课程的学生人数
SELECT
    a.c_id,
    a.c_name,
    count( 1 ) '报考人数' 
FROM
    course a
    INNER JOIN score b ON a.c_id = b.c_id 
GROUP BY
    a.c_id;

36、查询选修"张三"老师所授课程的学生中，成绩最高的学生信息及其成绩

-- 36、查询选修"张三"老师所授课程的学生中，成绩最高的学生信息及其成绩
SELECT
    d.*,
    c.c_id,
    b.c_name,
    c.s_score 
FROM
    teacher a
    INNER JOIN course b ON a.t_id = b.t_id 
    AND a.t_name = '张三'
    INNER JOIN score c ON b.c_id = c.c_id
    INNER JOIN student d ON c.s_id = d.s_id 
ORDER BY
    c.s_score DESC 
    LIMIT 1

37、查询不同课程成绩相同的学生的学生编号、课程编号、学生成绩(题意不清晰)

38、查询每门功成绩最好的前两名(重点)

-- 38、查询每门功成绩最好的前两名 
SELECT
    a.c_id,
    d.c_name,
    a.s_score,
    a.s_id,
    c.s_name 
FROM
    score a
    LEFT JOIN score b ON a.c_id = b.c_id 
    AND a.s_score < b.s_score
    INNER JOIN student c ON a.s_id = c.s_id
    INNER JOIN course d ON a.c_id = d.c_id 
GROUP BY
    a.c_id,
    a.s_id 
HAVING
    count( a.c_id )< 2;

这种方法的原理是查询同一门课程中，比自己分数高的学生的数量，第一名比自己高的数量为0，第二名为1，第三名为2.以此类推，所以只要查询count()<2即可

39、统计每门课程的学生选修人数

-- 39、统计每门课程的学生选修人数（超过5人的课程才统计）。要求输出课程号和选修人数，查询结果按人数降序排列，若人数相同，按课程号升序排列
SELECT
    c_id,
    count( 1 ) num 
FROM
    score 
GROUP BY
    c_id 
HAVING
    num > 5 
ORDER BY
    num DESC,
    c_id ASC;

40、检索至少选修两门课程的学生学号

-- 40、检索至少选修两门课程的学生学号
SELECT
    s_id 
FROM
    score 
GROUP BY
    s_id 
HAVING
    count( c_id )>= 2;

41、查询选修了全部课程的学生信息

-- 41、查询选修了全部课程的学生信息
select * from student where s_id in(select s_id from score group by s_id having count(c_id)=(select count(1) from course));

42、查询各学生的年龄(重点)

-- 42、查询各学生的年龄
    -- 按照出生日期来算，当前月日 < 出生年月的月日则，年龄减一
select s_id,s_name,DATE_FORMAT(NOW(),'%Y')-DATE_FORMAT(s_birth,'%Y')-(case when DATE_FORMAT(now(),'%m%d')<DATE_FORMAT(s_birth,'%m%d') then 1 else 0 end) age from student ;

43、查询本周过生日的学生

-- 43、查询本周过生日的学生
SELECT
    * 
FROM
    student 
WHERE
    WEEK (
        DATE_FORMAT( now(), '%Y%m%d' ))= WEEK (
        concat(
            DATE_FORMAT( now(), '%Y' ),
        DATE_FORMAT( s_birth, '-%m-%d' )));

现有问题:周日不算本周,算下周

44、查询下周过生日的学生

-- 44、查询下周过生日的学生
SELECT
    * 
FROM
    student 
WHERE
    (WEEK (
        DATE_FORMAT( now(), '%Y%m%d' ))+1)= (WEEK (
        concat(
            DATE_FORMAT( now(), '%Y' ),
        DATE_FORMAT( s_birth, '-%m-%d' ))));

WEEK(d),计算日期 d 是本年的第几个星期，范围是 0 到 53

DATE_FORMAT(d,f),按表达式 f的要求显示日期 d

45、查询本月过生日的学生

-- 45、查询本月过生日的学生
SELECT
    * 
FROM
    student 
WHERE
    DATE_FORMAT( s_birth, '%m' )= DATE_FORMAT(
    now(),
    '%m');

-- 45、查询本月过生日的学生
SELECT
    * 
FROM
    student 
WHERE
    MONTH ( s_birth )= MONTH (
    now());

MONTH(d),返回日期d中的月份值，1 到 12

NOW(),返回当前日期和时间

46、查询下月过生日的学生

-- 46、查询下月过生日的学生
SELECT
    * 
FROM
    student 
WHERE
    MONTH ( s_birth )= MONTH (
    now())+ 1;

posted @ 2022-05-08 21:08 进击的小蔡鸟阅读(236) 评论(0) 编辑收藏举报

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sql语句练习50题

sql语句练习50题

00 相关参考资料

01 表和测试数据

02 试题

1、查询"01"课程比"02"课程成绩高的学生的信息及课程分数

2、查询平均成绩大于60分的学生的学号和平均成绩

3、查询所有同学的学生编号、学生姓名、选课总数、所有课程的总成绩

4、查询"李"姓老师的数量

5、查询学过"张三"老师授课的同学的信息

6、查询没学过"张三"老师授课的同学的信息

7、查询学过编号为"01"并且也学过编号为"02"的课程的同学的信息

8、查询学过编号为"01"但是没有学过编号为"02"的课程的同学的信息

9、查询学全所有课程的同学的信息

10、查询至少有一门课与学号为"07"的同学所学相同的同学的信息

11、查询和"07"号的同学学习的课程完全相同的其他同学的信息

12、查询没学过"张三"老师讲授的任一门课程的学生姓名

13、查询两门及其以上不及格课程的同学的学号，姓名及其平均成绩

14、按平均成绩从高到低显示所有学生的所有课程的成绩以及平均成绩

15.查询各科成绩最高分、最低分和平均分

16、按各科成绩进行排序，并显示排名(未练习)

17、查询学生的总成绩并进行排名(未练习)

18、查询不同老师所教不同课程平均分从高到低显示

19、查询所有课程的成绩第2名到第3名的学生信息及该课程成绩(未练习)

20、统计各科成绩各分数段人数

21、查询学生平均成绩及其名次(未练习)

22、查询各科成绩前三名的记录(未练习)

23、查询每门课程被选修的学生数

24、查询出只有两门课程的全部学生的学号和姓名

25、查询男生、女生人数查询男生、女生人数

26、查询名字中含有"风"字的学生信息

27、查询同名同性学生名单，并统计同名人数

28、查询1990年出生的学生名单

29、查询每门课程的平均成绩，结果按平均成绩降序排列，平均成绩相同时，按课程编号升序排列

30、查询平均成绩大于等于80的所有学生的学号、姓名和平均成绩

31、查询所有学生的课程及分数情况；

32、查询任何一门课程成绩在70分以上的姓名、课程名称和分数；

33、查询不及格的课程(略)

34、查询课程编号为01且课程成绩在80分以上的学生的学号和姓名；

35、求每门课程的学生人数

36、查询选修"张三"老师所授课程的学生中，成绩最高的学生信息及其成绩

37、查询不同课程成绩相同的学生的学生编号、课程编号、学生成绩(题意不清晰)

38、查询每门功成绩最好的前两名(重点)

39、统计每门课程的学生选修人数

40、检索至少选修两门课程的学生学号

41、查询选修了全部课程的学生信息

42、查询各学生的年龄(重点)

43、查询本周过生日的学生

44、查询下周过生日的学生

45、查询本月过生日的学生

46、查询下月过生日的学生

公告

16、按各科成绩进行排序，并显示排名(`未练习`)

17、查询学生的总成绩并进行排名(`未练习`)

19、查询所有课程的成绩第2名到第3名的学生信息及该课程成绩(`未练习`)

21、查询学生平均成绩及其名次(`未练习`)

22、查询各科成绩前三名的记录(`未练习`)