-- 建立student和score表語句 DROPTABLEIFEXISTS t_student;CREATETABLE t_student(
id INT(10) AUTO_INCREMENT PRIMARYKEY,
name VARCHAR(200) NOTNULL,
sex VARCHAR(4),
birth YEAR,
department varchar(20) NOTNULL,
address VARCHAR(50)
);DROPTABLEIFEXISTS t_score;CREATETABLE t_score(
id INT(10) AUTO_INCREMENT PRIMARYKEY,
stu_id INT(10) NOTNULL,
c_name VARCHAR(20),
grade INT(10)
);-- 向student表插入記錄的insert語句如下:INSERTINTO t_student VALUES(901,'張老大','男',1985,'計算機系','北京市海淀區');INSERTINTO t_student VALUES( 902,'張老二', '男',1986,'中文系', '北京市昌平區');INSERTINTO t_student VALUES( 903,'張三', '女',1990,'中文系', '湖南省永州市');INSERTINTO t_student VALUES( 904,'李四', '男',1990,'英語系', '遼寧省阜新市');INSERTINTO t_student VALUES( 905,'王五', '女',1991,'英語系', '福建省廈門市');INSERTINTO t_student VALUES( 906,'王六', '男',1988,'計算機系', '湖南省衡陽市');-- 向score表插入記錄的INSERT語句如下:INSERTINTO t_score VALUES(NULL,901, '計算機',98);INSERTINTO t_score VALUES(NULL,901, '英語', 80);INSERTINTO t_score VALUES(NULL,902, '計算機',65);INSERTINTO t_score VALUES(NULL,902, '中文',88);INSERTINTO t_score VALUES(NULL,903, '中文',95);INSERTINTO t_score VALUES(NULL,904, '計算機',70);INSERTINTO t_score VALUES(NULL,904, '英語',92);INSERTINTO t_score VALUES(NULL,905, '英語',94);INSERTINTO t_score VALUES(NULL,906, '計算機',90);INSERTINTO t_score VALUES(NULL,906, '英語',85);-- 查詢student表的所有記錄 SELECT * FROM t_student;-- 查詢student表的第2條到4條記錄 SELECT * FROM t_student LIMIT 1,3;-- 從student表查詢所有學生的學號(id)、姓名(name)和院系(department)的資訊 SELECT id,name,department FROM t_student;-- 從student表中查詢計算機系和英語系的學生的資訊(用 IN 關鍵字)SELECT * FROM t_student WHERE department in ('計算機系','英語系');-- 從student表中查詢年齡18~22歲的學生資訊(用 BETWEEN AND) SELECT * FROM t_student
#WHERE (DATE_FORMAT(NOW(), '%Y') - birth)
WHERE (YEAR(NOW()) - birth)
BETWEEN 18AND42;-- 從student表中查詢每個院系有多少人SELECT department,COUNT(*)
FROM t_student
GROUPBY department;-- 從score表中查詢每個科目的最高分 SELECT s.c_name,MAX(s.grade)
FROM t_score AS s
WHERE s.c_name ISNOTNULLGROUPBY s.c_name;-- 查詢李四的考試科目(c_name)和考試成績(grade) SELECT s.`name`,e.c_name,e.grade
FROM t_score AS e
LEFTJOIN t_student AS s
ON e.stu_id = s.id
WHERE s.name = '李四';-- 用連線的方式查詢所有學生的資訊和考試資訊 SELECT *
FROM t_score AS e
LEFTJOIN t_student AS s
ON e.stu_id = s.id;-- 計算每個學生的總成績 SELECT stu_id,SUM(grade)
FROM t_score
GROUPBY stu_id;-- 計算每個考試科目的平均成績 SELECT c_name,AVG(grade)
FROM t_score
WHERE c_name ISNOTNULLGROUPBY c_name;-- 查詢計算機成績低於95的學生資訊 SELECT*
FROM t_score AS e
LEFTJOIN t_student AS s
ON e.stu_id = s.id
WHERE e.c_name = '計算機'AND e.grade < 95;
#方法二 考試科目沒有唯一性約束(可能存在補考,即同一個學生補考了兩次)
SELECT *
FROM t_student
WHERE id IN
(SELECT stu_id FROM t_score
WHERE c_name = '計算機'AND grade < 95);-- 查詢同時參加計算機和英語考試的學生的資訊SELECT * FROM t_student WHERE id = ANY
(
SELECT stu_id FROM t_score
WHERE stu_id IN(SELECT stu_id FROM t_score WHERE c_name = '計算機') AND c_name = '英語'
);
#方法二:
SELECT a.*
FROM t_student a,t_score b, t_score c
WHERE a.id = b.stu_id
AND b.c_name = '計算機'AND a.id = c.stu_id
AND c.c_name = '英語';-- 將計算機考試成績按從高到低進行排序 SELECT s.name,e.*
FROM t_score AS e
LEFTJOIN t_student AS s
ON e.stu_id = s.id
WHERE c_name = '計算機'ORDERBY grade DESC;-- 從student表和score表中查詢出學生的學號,然後合併查詢結果 SELECT s.id FROM t_student AS s
UNIONSELECT e.stu_id FROM t_score AS e;-- 查詢姓張或者姓王的同學的姓名、院系和考試科目及成績 SELECT s.name,s.department,e.c_name,e.grade
FROM t_score AS e
LEFTJOIN t_student AS s
ON e.stu_id = s.id
WHERE s.name LIKE'王%'OR s.name LIKE'張%';-- 查詢都是湖南的學生的姓名、年齡、院系和考試科目及成績SELECT s.name,(year(NOW()) - s.birth) AS age,s.department,e.c_name,e.grade
FROM t_score AS e
LEFTJOIN t_student AS s
ON e.stu_id = s.id
WHERE s.address LIKE'%湖南%';