MySQL講義第 47 講——select 查詢之查詢練習（五）
MySQL講義第 47 講——select 查詢之查詢練習（五）
以下查詢使用到四張表，分別是：student、teacher、course 和 electives，表結構如下：
CREATE TABLE student(
s_id char(5) primary key,
s_name char(20),
birth datetime,
phone char(20),
addr varchar(100)
);
INSERT INTO student
VALUES('S2011','張曉剛','1999-12-3','13163735775','信陽市'),
('S2012','劉小青','1999-10-11','13603732255','新鄉市'),
('S2013','曹夢德','1998-2-13','13853735522','鄭州市'),
('S2014','劉豔','1998-6-24','13623735335','鄭州市'),
('S2015','劉巖','1999-7-6','13813735225','信陽市'),
('S2016','劉若非','2000-8-31','13683735533','開封市'),
('S2021','董雯花','2000-7-30','13533735564','開封市'),
('S2022','周華建','1999-5-25','13243735578','鄭州市'),
('S2023','川普','1999-6-21','13343735588','新鄉市'),
('S2024','奧巴馬','2000-10-17','13843735885','信陽市'),
('S2025','周健華','2000-8-22','13788736655','開封市'),
('S2026','張學有','1998-7-6','13743735566','鄭州市'),
('S2031','李明博','1999-10-26','13643732222','鄭州市'),
('S2032','達芬奇','1999-12-31','13043731234','鄭州市'),
('S2033','李明博','1999-10-26','13643732222','鄭州市'),
('S2034','周健華','1999-12-31','13043731234','鄭州市'),
('S2035','張學有','1999-10-26','13643732222','鄭州市'),
('S2036','周健華','1999-12-31','13043731234','鄭州市');
CREATE TABLE teacher(
t_id char(5) primary key,
t_name char(20),
job_title char(20),
phone char(20)
);
INSERT INTO teacher
VALUES('T8001','歐陽修','教授','13703735666'),
('T8002','華羅庚','教授','13703735888'),
('T8003','鍾南山','教授','13703735675'),
('T8004','錢學森','教授','13703735638'),
('T8005','李白','副教授','13703735828'),
('T8006','孔子','教授','13703735457'),
('T8007','王安石','副教授','13703735369');
CREATE TABLE course(
c_id char(4) primary key,
c_name char(20),
t_id char(5)
);
INSERT INTO course
VALUES('C101','古代文學','T8001'),
('C102','高等數學','T8002'),
('C103','線性代數','T8002'),
('C104','臨床醫學','T8003'),
('C105','傳染病學','T8003'),
('C106','大學物理','T8004'),
('C107','詩歌欣賞','T8005'),
('C108','教育學','T8006'),
('C109','刑事訴訟法','T8007'),
('C110','經濟法','T8007');
CREATE TABLE score(
s_id char(5),
c_id char(4),
score int,
primary key(s_id, c_id)
);
INSERT INTO score
VALUES('S2011','C102',84),('S2011','C105',90),('S2011','C106',79),('S2011','C109',65),
('S2012','C101',67),('S2012','C102',52),('S2012','C103',55),('S2012','C104',86),
('S2012','C105',87),('S2012','C106',64),('S2012','C107',62),
('S2012','C108',73),('S2012','C109',78),('S2012','C110',89),
('S2013','C102',97),('S2013','C103',68),('S2013','C104',66),('S2013','C105',68),
('S2014','C102',90),('S2014','C103',85),('S2014','C104',77),('S2014','C105',96),
('S2015','C101',69),('S2015','C102',66),('S2015','C103',88),('S2015','C104',69),
('S2015','C105',66),('S2015','C106',88),('S2015','C107',69),
('S2015','C108',66),('S2015','C109',88),('S2015','C110',69),
('S2016','C101',65),('S2016','C102',69),('S2016','C107',82),('S2016','C108',56),
('S2021','C102',72),('S2021','C103',90),('S2021','C104',90),('S2021','C105',57),
('S2022','C102',88),('S2022','C103',93),('S2022','C109',47),('S2022','C110',62),
('S2023','C102',68),('S2023','C103',86),('S2023','C109',56),('S2023','C110',91),
('S2024','C102',87),('S2024','C103',97),('S2024','C109',80),('S2024','C110',81),
('S2025','C102',61),('S2025','C105',62),('S2025','C106',87),('S2025','C109',82),
('S2026','C102',59),('S2026','C105',48),('S2026','C106',90),('S2026','C109',73);
基於以上資料，完成如下查詢：
34、查詢每門課程選修的學生人數
SQL 語句如下：
SELECT
c.c_id,
c.c_name,
COUNT(*) AS cnt_stu
FROM
course c JOIN score sc
ON c.c_id = sc.c_id
GROUP BY
c.c_id
;
+------+-----------------+---------+
| c_id | c_name | cnt_stu |
+------+-----------------+---------+
| C101 | 古代文學 | 3 |
| C102 | 高等數學 | 12 |
| C103 | 線性代數 | 8 |
| C104 | 臨床醫學 | 5 |
| C105 | 傳染病學 | 8 |
| C106 | 大學物理 | 5 |
| C107 | 詩歌欣賞 | 3 |
| C108 | 教育學 | 3 |
| C109 | 刑事訴訟法 | 8 |
| C110 | 經濟法 | 5 |
+------+-----------------+---------+
10 rows in set (0.04 sec)
35、查詢選修了 4 門課程的學生的學號、姓名
SQL 語句如下：
SELECT
s.s_id,
s.s_name
FROM
student s JOIN score sc
ON s.s_id = sc.s_id
GROUP BY
s.s_id
HAVING
COUNT(*) = 4
;
+-------+-----------+
| s_id | s_name |
+-------+-----------+
| S2011 | 張曉剛 |
| S2013 | 曹夢德 |
| S2014 | 劉豔 |
| S2016 | 劉若非 |
| S2021 | 董雯花 |
| S2022 | 周華建 |
| S2023 | 川普 |
| S2024 | 奧巴馬 |
| S2025 | 周健華 |
| S2026 | 張學有 |
+-------+-----------+
10 rows in set (0.00 sec)
36、統計不同地區的學生人數
SQL 語句如下：
SELECT
addr,
COUNT(*) AS cnt_stu
FROM
student
GROUP BY
addr
;
+-----------+---------+
| addr | cnt_stu |
+-----------+---------+
| 信陽市 | 3 |
| 開封市 | 3 |
| 新鄉市 | 2 |
| 鄭州市 | 10 |
+-----------+---------+
4 rows in set (0.01 sec)
37、查詢姓【劉】的學生資訊
SQL 語句如下：
SELECT
s_id,
s_name,
phone,
addr
FROM
student
WHERE
s_name LIKE '劉%'
;
+-------+-----------+-------------+-----------+
| s_id | s_name | phone | addr |
+-------+-----------+-------------+-----------+
| S2012 | 劉小青 | 13603732255 | 新鄉市 |
| S2014 | 劉豔 | 13623735335 | 鄭州市 |
| S2015 | 劉巖 | 13813735225 | 信陽市 |
| S2016 | 劉若非 | 13683735533 | 開封市 |
+-------+-----------+-------------+-----------+
4 rows in set (0.05 sec)
38、查詢同名的學生資訊，並統計同名人數
SQL 語句如下：
SELECT
s_name,
COUNT(*) AS cnt
FROM
student
GROUP BY
s_name
HAVING
cnt > 1
;
+-----------+-----+
| s_name | cnt |
+-----------+-----+
| 周健華 | 3 |
| 張學有 | 2 |
| 李明博 | 2 |
+-----------+-----+
3 rows in set (0.01 sec)
SELECT
s1.s_id,
s1.s_name,
s1.birth,
s1.phone,
s1.addr,
s2.cnt
FROM
student s1 JOIN (SELECT s_name, COUNT(*) AS cnt
FROM student
GROUP BY s_name
HAVING cnt > 1) s2
ON s1.s_name = s2.s_name
ORDER BY
s_name
;
+-------+-----------+---------------------+-------------+-----------+-----+
| s_id | s_name | birth | phone | addr | cnt |
+-------+-----------+---------------------+-------------+-----------+-----+
| S2036 | 周健華 | 1999-12-31 00:00:00 | 13043731234 | 鄭州市 | 3 |
| S2034 | 周健華 | 1999-12-31 00:00:00 | 13043731234 | 鄭州市 | 3 |
| S2025 | 周健華 | 2000-08-22 00:00:00 | 13788736655 | 開封市 | 3 |
| S2026 | 張學有 | 1998-07-06 00:00:00 | 13743735566 | 鄭州市 | 2 |
| S2035 | 張學有 | 1999-10-26 00:00:00 | 13643732222 | 鄭州市 | 2 |
| S2031 | 李明博 | 1999-10-26 00:00:00 | 13643732222 | 鄭州市 | 2 |
| S2033 | 李明博 | 1999-10-26 00:00:00 | 13643732222 | 鄭州市 | 2 |
+-------+-----------+---------------------+-------------+-----------+-----+
7 rows in set (0.00 sec)
39、查詢 1998 年出生的學生資訊
SQL 語句如下：
SELECT
s_id,
s_name,
birth,
phone,
addr
FROM
student
WHERE
birth BETWEEN '1998-1-1' AND '1998-12-31'
;
+-------+-----------+---------------------+-------------+-----------+
| s_id | s_name | birth | phone | addr |
+-------+-----------+---------------------+-------------+-----------+
| S2013 | 曹夢德 | 1998-02-13 00:00:00 | 13853735522 | 鄭州市 |
| S2014 | 劉豔 | 1998-06-24 00:00:00 | 13623735335 | 鄭州市 |
| S2026 | 張學有 | 1998-07-06 00:00:00 | 13743735566 | 鄭州市 |
+-------+-----------+---------------------+-------------+-----------+
3 rows in set (0.01 sec)
40、查詢每門課程的平均成績，按平均成績降序排列，平均成績相同時，按課程編號升序排列
SQL 語句如下：
SELECT
c.c_id,
c.c_name,
AVG(score) AS avg_score
FROM
course c JOIN score sc
ON c.c_id = sc.c_id
GROUP BY
c.c_id
ORDER BY
avg_score DESC, c.c_id
;
+------+-----------------+-----------+
| c_id | c_name | avg_score |
+------+-----------------+-----------+
| C103 | 線性代數 | 82.7500 |
| C106 | 大學物理 | 81.6000 |
| C110 | 經濟法 | 78.4000 |
| C104 | 臨床醫學 | 77.6000 |
| C102 | 高等數學 | 74.4167 |
| C105 | 傳染病學 | 71.7500 |
| C109 | 刑事訴訟法 | 71.1250 |
| C107 | 詩歌欣賞 | 71.0000 |
| C101 | 古代文學 | 67.0000 |
| C108 | 教育學 | 65.0000 |
+------+-----------------+-----------+
10 rows in set (0.03 sec)
41、查詢平均成績 80 分以上（包含 80）的所有學生的學號、姓名和平均成績
SQL 語句如下：
SELECT
s.s_id,
s.s_name,
AVG(score) AS avg_score
FROM
student s JOIN score sc
ON s.s_id = sc.s_id
GROUP BY
s.s_id
HAVING
avg_score >= 80
;
+-------+-----------+-----------+
| s_id | s_name | avg_score |
+-------+-----------+-----------+
| S2014 | 劉豔 | 87.0000 |
| S2024 | 奧巴馬 | 86.2500 |
+-------+-----------+-----------+
2 rows in set (0.00 sec)
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