數據庫練習題

-- 班級表 CREATE TABLE CLASS( classid VARCHAR(3) PRIMARY KEY, `subject` VARCHAR(20) NOT NULL DEFAULT '', deptname VARCHAR(20) NOT NULL DEFAULT '', enrolltime YEAR NOT NULL DEFAULT 9, num INTEGER NOT NULL DEFAULT 0, FOREIGN KEY (deptname) REFERENCES DEPARTMENT(deptname) );-- 學生表 CREATE TABLE STUDENTS( studentid VARCHAR(4) PRIMARY KEY, `name` VARCHAR(20) NOT NULL DEFAULT '', age INTEGER NOT NULL DEFAULT 0, classid VARCHAR(3), FOREIGN KEY (classid) REFERENCES CLASS(classid));-- 系表 CREATE TABLE DEPARTMENT( departmentid VARCHAR(4) PRIMARY KEY, deptname VARCHAR(20) UNIQUE NOT NULL DEFAULT '');-- 插入數據 INSERT INTO DEPARTMENT VALUES(001,'數學'); INSERT INTO DEPARTMENT VALUES(002,'計算機'); INSERT INTO DEPARTMENT VALUES(003,'化學'); INSERT INTO DEPARTMENT VALUES(004,'中文'); INSERT INTO DEPARTMENT VALUES(005,'經濟');INSERT INTO class VALUES(101,'軟件','計算機',1995,20); INSERT INTO class VALUES(102,'微電子','計算機',1996,30); INSERT INTO class VALUES(111,'無機化學','化學',1995,29); INSERT INTO class VALUES(112,'高分子化學','化學',1996,25); INSERT INTO class VALUES(121,'統計數學','數學',1995,20); INSERT INTO class VALUES(131,'現代語言','中文',1996,20); INSERT INTO class VALUES(141,'國際貿易','經濟',1997,30); INSERT INTO class VALUES(142,'國際金融','經濟',1996,14);INSERT INTO hsp_student VALUES(8101,'張三',18,101); INSERT INTO hsp_student VALUES(8102,'錢四',16,121); INSERT INTO hsp_student VALUES(8103,'王玲',17,131); INSERT INTO hsp_student VALUES(8105,'李飛',19,102); INSERT INTO hsp_student VALUES(8109,'趙四',18,141); INSERT INTO hsp_student VALUES(8110,'李可',20,142); INSERT INTO hsp_student VALUES(8201,'張飛',18,111); INSERT INTO hsp_student VALUES(8302,'周瑜',16,112); INSERT INTO hsp_student VALUES(8203,'王亮',17,111); INSERT INTO hsp_student VALUES(8305,'董慶',19,102); INSERT INTO hsp_student VALUES(8409,'趙龍',18,101); -- 3.1 SELECT * FROM STUDENTSWHERE `name` LIKE '李%'-- 3.2 SELECT COUNT(DISTINCT subject) AS nums, deptname FROM classGROUP BY deptname HAVING nums > 1-- 3.3 列出人數大于等于30的系的編號和名字。 -- 1. 先查出各個系有多少人, 并得到 >= 30 的系 SELECT SUM(num) AS nums, deptname FROM class GROUP BY deptname HAVING nums >= 30-- 2. 將上面的結果看成一個臨時表 和 department 聯合查詢即可 SELECT tmp.*, department.departmentidFROM department , (SELECT SUM(num) AS nums, deptname FROM class GROUP BY deptname HAVING nums >= 30) tmp WHERE department.deptname = tmp.deptname;-- (4) 學校又新增加了一個物理系，編號為006 -- 添加一條數據 INSERT INTO department VALUES('006','物理系');-- (5) 學生張三退學，請更新相關的表 -- 分析：1. 張三所在班級的人數-1 -- 2. 將張三從學生表刪除 -- 3. 需要使用事務控制 -- 開啟事務 START TRANSACTION; -- 張三所在班級的人數-1 UPDATE class SET num = num - 1WHERE classid = (SELECT classid FROM students WHERE NAME = '張三');DELETE FROM studentsWHERE NAME = '張三';-- 提交事務 COMMIT;

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