【数据库——MySQL】（11）查询和视图练习及讲解
目录
- 1. 简述
- 2. 题目
-
- 2.1 查询
- 2.2 视图的使用
-
- 2.2.1 创建视图
- 2.2.2 查询视图
- 2.2.3 更新视图
- 2.2.4 删除视图
- 3. 解答
-
- 3.1 查询
- 3.2 视图的使用
-
- 3.2.1 创建视图
- 3.2.2 查询视图
- 3.2.3 更新视图
- 3.2.4 删除视图
1. 简述
在前面我们也给出了一些查询的练习题供大家练习，这里再给出进阶版的查询练习给大家练练手，同时还会给出上一篇文章视图的对应习题！
2. 题目
2.1 查询
先建立数据库 score，代码如下：
# 先删除数据库
DROP DATABASE IF EXISTS score;
# 创建数据库
CREATE DATABASE IF NOT EXISTS `score`
DEFAULT CHARACTER SET 'gb18030'
DEFAULT COLLATE 'gb18030_chinese_ci';
USE score;
SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;
-- ----------------------------
-- Table structure for department
-- ----------------------------
DROP TABLE IF EXISTS `department`;
CREATE TABLE `department` (
`id` char(4) CHARACTER SET gbk COLLATE gbk_chinese_ci NOT NULL,
`name` varchar(20) CHARACTER SET gbk COLLATE gbk_chinese_ci NULL DEFAULT NULL,
PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = gbk COLLATE = gbk_chinese_ci ROW_FORMAT = Dynamic;
-- ----------------------------
-- Records of department
-- ----------------------------
INSERT INTO `department` VALUES ('101', '数学学院');
INSERT INTO `department` VALUES ('102', '计算机学院');
INSERT INTO `department` VALUES ('103', '外语学院');
INSERT INTO `department` VALUES ('104', '物理学院');
INSERT INTO `department` VALUES ('105', '电气学院');
INSERT INTO `department` VALUES ('106', '马克思主义学院');
INSERT INTO `department` VALUES ('107', '哲学院');
INSERT INTO `department` VALUES ('108', '体育学院');
INSERT INTO `department` VALUES ('109', '土木学院');
INSERT INTO `department` VALUES ('110', '遥感学院');
-- ----------------------------
-- Table structure for grade
-- ----------------------------
DROP TABLE IF EXISTS `grade`;
CREATE TABLE `grade` (
`grade` char(2) CHARACTER SET gbk COLLATE gbk_chinese_ci NOT NULL DEFAULT '',
`lowScore` int(0) NULL DEFAULT NULL,
`highScore` int(0) NULL DEFAULT NULL,
PRIMARY KEY (`grade`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = gbk COLLATE = gbk_chinese_ci ROW_FORMAT = Dynamic;
-- ----------------------------
-- Records of grade
-- ----------------------------
INSERT INTO `grade` VALUES ('A', 90, 100);
INSERT INTO `grade` VALUES ('B', 80, 89);
INSERT INTO `grade` VALUES ('C', 70, 79);
INSERT INTO `grade` VALUES ('D', 60, 69);
INSERT INTO `grade` VALUES ('E', 0, 59);
-- ----------------------------
-- Table structure for lesson
-- ----------------------------
DROP TABLE IF EXISTS `lesson`;
CREATE TABLE `lesson` (
`lessonid` int(0) NOT NULL,
`lessonName` varchar(20) CHARACTER SET gbk COLLATE gbk_chinese_ci NULL DEFAULT NULL,
`xf` int(0) GENERATED ALWAYS AS ((`time` / 16)) STORED NULL,
`deparmentId` char(5) CHARACTER SET gbk COLLATE gbk_chinese_ci NOT NULL,
`preLessonId` int(0) NULL DEFAULT NULL,
`time` int(0) NULL DEFAULT NULL,
INDEX `lessonid`(`lessonid`) USING BTREE,
INDEX `ix_name`(`lessonName`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = gbk COLLATE = gbk_chinese_ci ROW_FORMAT = Dynamic;
-- ----------------------------
-- Records of lesson
-- ----------------------------
INSERT INTO `lesson` VALUES (101, '数学', DEFAULT, '101', NULL, 72);
INSERT INTO `lesson` VALUES (102, '英语', DEFAULT, '102', NULL, 96);
INSERT INTO `lesson` VALUES (103, '程序设计', DEFAULT, '103', 101, 64);
INSERT INTO `lesson` VALUES (104, '物理', DEFAULT, '104', 101, 32);
INSERT INTO `lesson` VALUES (105, '政治', DEFAULT, '106', NULL, 80);
INSERT INTO `lesson` VALUES (106, '法语', DEFAULT, '102', 102, NULL);
INSERT INTO `lesson` VALUES (107, '体育', DEFAULT, '108', NULL, 96);
INSERT INTO `lesson` VALUES (108, '地理信息系统', DEFAULT, '110', 103, 32);
INSERT INTO `lesson` VALUES (109, '数据库', DEFAULT, '103', 103, 48);
-- ----------------------------
-- Table structure for score
-- ----------------------------
DROP TABLE IF EXISTS `score`;
CREATE TABLE `score` (
`Id` int(0) NOT NULL AUTO_INCREMENT,
`stuId` char(13) CHARACTER SET gbk COLLATE gbk_chinese_ci NOT NULL,
`LessonId` int(0) NOT NULL,
`score` int(0) NULL DEFAULT 0,
PRIMARY KEY (`Id`) USING BTREE,
INDEX `课程`(`LessonId`) USING BTREE,
INDEX `fk-stu`(`stuId`) USING BTREE,
CONSTRAINT `fk-stu` FOREIGN KEY (`stuId`) REFERENCES `stu` (`id`) ON DELETE CASCADE ON UPDATE CASCADE,
CONSTRAINT `课程` FOREIGN KEY (`LessonId`) REFERENCES `lesson` (`lessonid`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE = InnoDB AUTO_INCREMENT = 57 CHARACTER SET = gbk COLLATE = gbk_chinese_ci ROW_FORMAT = Dynamic;
-- ----------------------------
-- Records of score
-- ----------------------------
INSERT INTO `score` VALUES (1, '20201001', 103, 99);
INSERT INTO `score` VALUES (2, '20201002', 101, 77);
INSERT INTO `score` VALUES (3, '20201001', 101, 65);
INSERT INTO `score` VALUES (4, '20201003', 101, 88);
INSERT INTO `score` VALUES (5, '20201002', 102, 98);
INSERT INTO `score` VALUES (6, '20211001', 103, 91);
INSERT INTO `score` VALUES (7, '20191002', 102, 82);
INSERT INTO `score` VALUES (8, '20191002', 101, 63);
INSERT INTO `score` VALUES (9, '20201003', 103, 71);
INSERT INTO `score` VALUES (10, '20201001', 104, 72);
INSERT INTO `score` VALUES (11, '20201003', 104, 94);
INSERT INTO `score` VALUES (12, '20201003', 102, 77);
INSERT INTO `score` VALUES (13, '20201004', 103, 82);
INSERT INTO `score` VALUES (14, '20211001', 104, 78);
INSERT INTO `score` VALUES (15, '20191003', 104, 74);
INSERT INTO `score` VALUES (16, '20211002', 102, 87);
INSERT INTO `score` VALUES (17, '20211001', 102, 51);
INSERT INTO `score` VALUES (18, '20201004', 101, 86);
INSERT INTO `score` VALUES (19, '20201001', 102, 84);
INSERT INTO `score` VALUES (20, '20201002', 103, 94);
INSERT INTO `score` VALUES (21, '20201002', 104, 48);
INSERT INTO `score` VALUES (29, '20191001', 101, 85);
INSERT INTO `score` VALUES (30, '20211002', 104, 82);
INSERT INTO `score` VALUES (31, '20191001', 103, 90);
INSERT INTO `score` VALUES (34, '20191004', 101, 68);
INSERT INTO `score` VALUES (35, '20211003', 102, 80);
INSERT INTO `score` VALUES (36, '20191004', 103, 83);
INSERT INTO `score` VALUES (37, '20191004', 105, 91);
INSERT INTO `score` VALUES (38, '20211002', 105, 84);
INSERT INTO `score` VALUES (39, '20211001', 105, 70);
INSERT INTO `score` VALUES (40, '20191004', 105, 88);
INSERT INTO `score` VALUES (46, '20211003', 104, 56);
INSERT INTO `score` VALUES (47, '20211003', 105, 76);
INSERT INTO `score` VALUES (48, '20211002', 101, 86);
INSERT INTO `score` VALUES (49, '20211001', 101, 76);
INSERT INTO `score` VALUES (50, '20211001', 104, 96);
INSERT INTO `score` VALUES (55, '20211003', 105, 90);
INSERT INTO `score` VALUES (56, '20211001', 106, 78);
INSERT INTO `score` VALUES (57, '20221203', 103, 88);
INSERT INTO `score` VALUES (58, '20221203', 102, 50);
-- ----------------------------
-- Table structure for stu
-- ----------------------------
DROP TABLE IF EXISTS `stu`;
CREATE TABLE `stu` (
`id` char(13) CHARACTER SET gbk COLLATE gbk_chinese_ci NOT NULL,
`name` char(10) CHARACTER SET gbk COLLATE gbk_chinese_ci NULL DEFAULT NULL,
`sex` enum('男','女') CHARACTER SET gbk COLLATE gbk_bin NULL DEFAULT '男',
`departmentId` char(5) CHARACTER SET gbk COLLATE gbk_chinese_ci NOT NULL DEFAULT '',
`birthday` date NULL DEFAULT NULL,
`hoppy` set('打球','跳舞','游戏','逛街','唱歌') CHARACTER SET gbk COLLATE gbk_chinese_ci NULL DEFAULT NULL,
`address` json NULL,
PRIMARY KEY (`id`) USING BTREE,
INDEX `fk-department`(`departmentId`) USING BTREE,
CONSTRAINT `fk-department` FOREIGN KEY (`departmentId`) REFERENCES `department` (`id`) ON DELETE RESTRICT ON UPDATE CASCADE
) ENGINE = InnoDB CHARACTER SET = gbk COLLATE = gbk_chinese_ci ROW_FORMAT = Dynamic;
-- ----------------------------
-- Records of stu
-- ----------------------------
INSERT INTO `stu` VALUES ('20191001', '许和雅', '女', '102', '2001-01-12', '打球,游戏', '{\"tel\": \"18927763056\", \"name\": \"John\", \"address\": \"Beijing\"}');
INSERT INTO `stu` VALUES ('20191002', '冯红云', '女', '103', '2001-05-10', '打球', '{\"tel\": \"13908623506\", \"name\": \"Alice\", \"address\": \"ShangHai\"}');
INSERT INTO `stu` VALUES ('20191003', '冯海', '男', '103', NULL, '逛街', NULL);
INSERT INTO `stu` VALUES ('20191004', '刘一凡', '男', '105', NULL, '打球,跳舞,游戏', '{\"tel\": \"13702345067\", \"name\": \"Bob\", \"address\": \"Wuhan\"}');
INSERT INTO `stu` VALUES ('20191011', 'Alice', '女', '102', '1999-12-14', '打球,跳舞,逛街', NULL);
INSERT INTO `stu` VALUES ('20191012', 'john', '男', '103', '2000-02-05', NULL, NULL);
INSERT INTO `stu` VALUES ('20201001', '张三', '男', '101', NULL, '打球,逛街', NULL);
INSERT INTO `stu` VALUES ('20201002', '李四', '男', '102', '2001-01-12', '跳舞,逛街', NULL);
INSERT INTO `stu` VALUES ('20201003', '王五', '女', '103', NULL, '打球,跳舞,逛街', NULL);
INSERT INTO `stu` VALUES ('20201004', '赵六', '女', '101', NULL, '游戏,逛街', NULL);
INSERT INTO `stu` VALUES ('20201005', '张海', '男', '104', NULL, NULL, '{\"tel\": \"18985107123\", \"name\": \"abc\", \"address\": \"Wuhan\"}');
INSERT INTO `stu` VALUES ('20201006', '张三丰', '男', '105', '2000-09-20', '跳舞,唱歌', NULL);
INSERT INTO `stu` VALUES ('20201008', '陈启', '女', '105', NULL, NULL, '{\"tel\": \"13521234567\", \"address\": \"ShangHai\"}');
INSERT INTO `stu` VALUES ('20211001', '韦俊豪', '男', '101', '2002-03-02', NULL, NULL);
INSERT INTO `stu` VALUES ('20211002', '雷淳雅', '女', '101', NULL, '跳舞,游戏', '{\"tel\": \"13707761223\", \"name\": \"sunny\", \"address\": \"Shenzhen\"}');
INSERT INTO `stu` VALUES ('20211003', '李磊', '男', '104', NULL, '跳舞,逛街', NULL);
INSERT INTO `stu` VALUES ('20221201', '郭靖', '男', '103', '2020-03-10', NULL, '{\"tel\": \"17725108427\", \"name\": \"guo\", \"address\": \"Chengdu\"}');
INSERT INTO `stu` VALUES ('20221202', '黄蓉', '男', '106', '2020-04-10', NULL, '{\"tel\": \"17715108427\", \"name\": \"huang\", \"address\": \"changsha\"}');
INSERT INTO `stu` VALUES ('20221203', 'Mary', '女', '103', NULL, NULL, NULL);
-- ----------------------------
-- View structure for v_stu
-- ----------------------------
DROP VIEW IF EXISTS `v_stu`;
CREATE ALGORITHM = UNDEFINED SQL SECURITY DEFINER VIEW `v_stu` AS select `stu`.`id` AS `id`,`stu`.`name` AS `name`,`department`.`name` AS `院系`,`lesson`.`lessonName` AS `课程`,`score`.`score` AS `成绩` from (((`stu` join `department` on((`stu`.`departmentId` = `department`.`id`))) left join `score` on((`stu`.`id` = `score`.`stuId`))) left join `lesson` on((`score`.`LessonId` = `lesson`.`lessonid`)));
-- ----------------------------
-- Records of stu
-- ----------------------------
INSERT INTO `stu` VALUES ('20191001', '许和雅', '计算机学院', '数学', 85);
INSERT INTO `stu` VALUES ('20191001', '许和雅', '计算机学院', '程序设计', 90);
INSERT INTO `stu` VALUES ('20191002', '冯红云', '外语学院', '英语', 82);
INSERT INTO `stu` VALUES ('20191002', '冯红云', '外语学院', '数学', 63);
INSERT INTO `stu` VALUES ('20191003', '冯海', '外语学院', '物理', 74);
INSERT INTO `stu` VALUES ('20191004', '刘一凡', '电气学院', '数学', 68);
INSERT INTO `stu` VALUES ('20191004', '刘一凡', '电气学院', '程序设计', 83);
INSERT INTO `stu` VALUES ('20191004', '刘一凡', '电气学院', '政治', 91);
INSERT INTO `stu` VALUES ('20191004', '刘一凡', '电气学院', '政治', 88);
INSERT INTO `stu` VALUES ('20191011', 'Alice', '计算机学院', NULL, NULL);
INSERT INTO `stu` VALUES ('20191012', 'john', '外语学院', NULL, NULL);
INSERT INTO `stu` VALUES ('20201001', '张三', '数学学院', '程序设计', 99);
INSERT INTO `stu` VALUES ('20201001', '张三', '数学学院', '数学', 65);
INSERT INTO `stu` VALUES ('20201001', '张三', '数学学院', '物理', 72);
INSERT INTO `stu` VALUES ('20201001', '张三', '数学学院', '英语', 84);
INSERT INTO `stu` VALUES ('20201002', '李四', '计算机学院', '数学', 77);
INSERT INTO `stu` VALUES ('20201002', '李四', '计算机学院', '英语', 98);
INSERT INTO `stu` VALUES ('20201002', '李四', '计算机学院', '程序设计', 94);
INSERT INTO `stu` VALUES ('20201002', '李四', '计算机学院', '物理', 48);
INSERT INTO `stu` VALUES ('20201003', '王五', '外语学院', '数学', 88);
INSERT INTO `stu` VALUES ('20201003', '王五', '外语学院', '程序设计', 71);
INSERT INTO `stu` VALUES ('20201003', '王五', '外语学院', '物理', 94);
INSERT INTO `stu` VALUES ('20201003', '王五', '外语学院', '英语', 77);
INSERT INTO `stu` VALUES ('20201004', '赵六', '数学学院', '程序设计', 82);
INSERT INTO `stu` VALUES ('20201004', '赵六', '数学学院', '数学', 86);
INSERT INTO `stu` VALUES ('20201005', '张海', '物理学院', NULL, NULL);
INSERT INTO `stu` VALUES ('20201006', '张三丰', '电气学院', NULL, NULL);
INSERT INTO `stu` VALUES ('20201008', '陈启', '电气学院', NULL, NULL);
INSERT INTO `stu` VALUES ('20211001', '韦俊豪', '数学学院', '程序设计', 91);
INSERT INTO `stu` VALUES ('20211001', '韦俊豪', '数学学院', '物理', 78);
INSERT INTO `stu` VALUES ('20211001', '韦俊豪', '数学学院', '英语', 51);
INSERT INTO `stu` VALUES ('20211001', '韦俊豪', '数学学院', '政治', 70);
INSERT INTO `stu` VALUES ('20211001', '韦俊豪', '数学学院', '数学', 76);
INSERT INTO `stu` VALUES ('20211001', '韦俊豪', '数学学院', '物理', 96);
INSERT INTO `stu` VALUES ('20211001', '韦俊豪', '数学学院', '法语', 78);
INSERT INTO `stu` VALUES ('20211002', '雷淳雅', '数学学院', '英语', 87);
INSERT INTO `stu` VALUES ('20211002', '雷淳雅', '数学学院', '物理', 82);
INSERT INTO `stu` VALUES ('20211002', '雷淳雅', '数学学院', '政治', 84);
INSERT INTO `stu` VALUES ('20211002', '雷淳雅', '数学学院', '数学', 86);
INSERT INTO `stu` VALUES ('20211003', '李磊', '物理学院', '英语', 80);
INSERT INTO `stu` VALUES ('20211003', '李磊', '物理学院', '物理', 56);
INSERT INTO `stu` VALUES ('20211003', '李磊', '物理学院', '政治', 76);
INSERT INTO `stu` VALUES ('20211003', '李磊', '物理学院', '政治', 90);
INSERT INTO `stu` VALUES ('20221201', '郭靖', '外语学院', NULL, NULL);
INSERT INTO `stu` VALUES ('20221202', '黄蓉', '马克思主义学院', NULL, NULL);
INSERT INTO `stu` VALUES ('20221203', 'Mary', '外语学院', '程序设计', 88);
INSERT INTO `stu` VALUES ('20221203', 'Mary', '外语学院', '英语', 50);
-- ----------------------------
-- View structure for v_sum_score
-- ----------------------------
DROP VIEW IF EXISTS `v_sum_score`;
CREATE ALGORITHM = UNDEFINED SQL SECURITY DEFINER VIEW `v_sum_score` AS select `stu`.`id` AS `id`,`stu`.`name` AS `Name`,sum(`score`.`score`) AS `SumScore` from (`stu` join `score` on((`stu`.`id` = `score`.`stuId`))) group by `stu`.`id`;
-- ----------------------------
-- Records of stu
-- ----------------------------
INSERT INTO `stu` VALUES ('20201001', '张三', 320);
INSERT INTO `stu` VALUES ('20201002', '李四', 317);
INSERT INTO `stu` VALUES ('20201003', '王五', 330);
INSERT INTO `stu` VALUES ('20211001', '韦俊豪', 540);
INSERT INTO `stu` VALUES ('20191002', '冯红云', 145);
INSERT INTO `stu` VALUES ('20201004', '赵六', 168);
INSERT INTO `stu` VALUES ('20191003', '冯海', 74);
INSERT INTO `stu` VALUES ('20211002', '雷淳雅', 339);
INSERT INTO `stu` VALUES ('20191001', '许和雅', 175);
INSERT INTO `stu` VALUES ('20191004', '刘一凡', 330);
INSERT INTO `stu` VALUES ('20211003', '李磊', 302);
INSERT INTO `stu` VALUES ('20221203', 'Mary', 138);
SET FOREIGN_KEY_CHECKS = 1;
-
查询显示成绩表中的最高分，平均分。
-
查询学生的学号，姓名 和 出生日期，按院系编号降序。
-
查询所有学生的学号，姓名和院系名。
-
查询参加了高等数学课程的考试的学生姓名和考试成绩。
-
查询每个学院的学生人数。
-
查询平均分最高的
5名学生的学号，姓名和平均分。 -
查询总学分高于
10分的所有学生。 -
查询数学学院的学生的学号，姓名，所选课程的成绩和等级,并按成绩从高到低排序。
-
查询数学学院的学生的学号，姓名，获得的学分并按学分从高到低排序。
-
查询英语成绩最高的学生的学号，姓名，所有功课的成绩和所在学院。
-
查询比计算机学院所有学生的总分都高的数学学院的学生的学号，姓名和总分。
2.2 视图的使用
此题需要用到数据库 YGGL，此数据库再前面给出的习题中已创建，未创建此数据库的同学请运行下述代码创建，已经创建的同学可以跳过此步骤！
drop database if exists yggl;
create database if not exists yggl;
USE yggl;
drop table if exists departments;
CREATE TABLE Departments(
DepartmentID char(3) NOT NULL PRIMARY KEY COMMENT '部门编号',
DepartmentName char(20) NOT NULL COMMENT '部门名',
Note text NULL COMMENT '备注'
);
drop table if exists salary;
CREATE TABLE Salary(
EmployeeID char(6) NOT NULL PRIMARY KEY COMMENT '员工编号',
InCome float NOT NULL COMMENT '收入',
OutCome float NOT NULL COMMENT '支出'
);
drop table if exists employees;
CREATE TABLE Employees(
EmployeeID char(6) NOT NULL PRIMARY KEY COMMENT '员工编号',
Name char(10) NOT NULL COMMENT '姓名',
Education char(4) NOT NULL COMMENT '学历',
Birthday date NOT NULL COMMENT '出生日期',
Sex char(2) NOT NULL COMMENT '性别',
WorkYear tinyint(1) COMMENT '工作时间',
Address char(20) NULL COMMENT '地址',
PhoneNumber char(12) NULL COMMENT '电话号码',
DepartmentID char(3) NOT NULL COMMENT '部门编号'
);
insert into Departments
values('1','财务部',null),
('2','人力资源部',null),
('3','经理办公室',null),
('4','研发部',null),
('5','市场部',null)
;
insert into Employees values
('000001','王林','大专','1966-1-23',1,8,'中山路32-1-508','83355668','2'),
('010008','伍容华','本科','1976-3-28',1,3,'北京东路100-2','83321321','1'),
('020010','王向蓉','硕士','1982-12-9',1,2,'四牌楼10-10-108','83792361','1'),
('020018','李丽','大专','1960-7-30',0,6,'中山东路102-2','83413301','1'),
('102201','刘明','本科','1972-10-18',1,3,'虎踞路100-2','83606608','5'),
('102208','朱骏','硕士','1965-9-28',1,2,'牌楼巷5-3-106','84708817','5'),
('108991','钟敏','硕士','1979-8-10',0,4,'中山路10-3-105','83346722','3'),
('111006','张石兵','本科','1974-10-1',1,1,'解放路34-1-203','84563418','5'),
('210678','林涛','大专','1977-4-2',1,2,'中山北路24-35','83467336','3'),
('302566','李玉珉','本科','1968-9-20',1,3,'热河路209-3','58765991','4'),
('308759','叶凡','本科','1978-11-18',1,2,'北京西路3-7-52','83308901','4'),
('504209','陈林琳','大专','1969-9-3',0,5,'汉中路120-4-12','84468158','4')
;
insert into Salary values
('000001',2100.8,123.09),
('010008',1582.62,88.03),
('102201',2569.88,185.65),
('111006',1987.01,79.58),
('504209',2066.15,108),
('302566',2980.7,210.2),
('108991',3259.98,281.52),
('020010',2860,198),
('020018',2347.68,180),
('308759',2531.98,199.08),
('210678',2240,121),
('102208',1980,100)
;
2.2.1 创建视图
-
在
YGGL数据库创建视图ds_view，视图包含Departments表的全部列。 -
在
YGGL数据库创建视图Employees_view，视图包含员工号码、姓名和实际收入。 -
创建视图，包含员工号码、姓名、所在部门名称和实际收入列。
2.2.2 查询视图
-
从视图
ds_view中查询出部门号为3的部门名称。 -
从视图
Employees_view中查询出姓名为“王林”的员工的实际收入。
2.2.3 更新视图
-
向视图
ds_view中插入一行数据：6，财务部，财务管理。 -
尝试向视图
Employees_view中插入一行数据，看看会发生什么。
insert into Employees_view values('100000', '邓文辉', '9999'); -
修改视图
ds_view，将部门号为5的部门名称修改为“生产车间”。 -
修改视图
Employees_view中号码为“000001”的员工的姓名为“王浩”。 -
删除视图
ds_view中部门号为“1”的数据。
2.2.4 删除视图
- 删除视图
ds_view。
3. 解答
3.1 查询
-
查询显示成绩表中的最高分，平均分。
select max(score) as 最高分, avg(score) as 平均分 from score; -
查询学生的学号，姓名 和 出生日期，按院系编号降序。
select id, `name`, birthday from stu ORDER BY departmentId desc; -
查询所有学生的学号，姓名和院系名。
select stu.id as 学号, stu.`name` as 姓名, department.`name` as 院系 from stu join department on stu.departmentId = department.id; -
查询参加了高等数学课程的考试的学生姓名和考试成绩。
select stu.`name`, score.score from stu join score on stu.id = score.stuId join lesson on score.LessonId = lesson.lessonid where lesson.lessonName = '数学'; -
查询每个学院的学生人数。
select department.`name` as 院系, count(*) as 学生人数 from department join stu on department.id = stu.departmentId GROUP BY department.`name`; -
查询平均分最高的
5名学生的学号，姓名和平均分。select stu.id, stu.`name`, avg(score.score) as 平均分 from stu join score on stu.id = score.stuId GROUP BY stu.id ORDER BY avg(score.score) desc limit 5; -
查询总学分高于
10分的所有学生。select stu.`name`, sum(if(score.score >= 60, lesson.xf, 0)) as 学分 from stu join score on stu.id = score.stuid join lesson on score.lessonid = lesson.lessonid GROUP BY stu.`name` having sum(if(score.score >= 60, lesson.xf, 0)) > 10; -
查询数学学院的学生的学号，姓名，所选课程的成绩和等级,并按成绩从高到低排序。
select stu.id, stu.`name`, lesson.lessonName, score.score, grade.grade from score join stu on score.stuid = stu.id join lesson on score.LessonId = lesson.lessonid join department on stu.departmentId = department.id join grade on score.score BETWEEN grade.lowScore and grade.highScore where department.`name` = '数学学院' ORDER BY score.score desc; -
查询数学学院的学生的学号，姓名，获得的学分并按学分从高到低排序。
select stu.id, stu.`name`, sum(if(score.score >= 60, lesson.xf, 0)) as 学分 from stu join score on stu.id = score.stuid join lesson on score.LessonId = lesson.lessonid join department on stu.departmentId = department.id where department.`name` = '数学学院' GROUP BY stu.id ORDER BY 学分 desc; -
查询英语成绩最高的学生的学号，姓名，所有功课的成绩和所在学院。
select stu.id, stu.`name`, score.score, department.`name` as 院系 from stu join score on stu.id = score.stuId join department on stu.departmentId = department.id where stu.id = ( select stu.id from stu join score on stu.id = score.stuId join lesson on score.LessonId = lesson.lessonid where lesson.lessonName = '英语' ORDER BY score.score desc limit 1 ); -
查询比计算机学院所有学生的总分都高的数学学院的学生的学号，姓名和总分。
select stu.id, stu.`name`, sum(score.score) as 总分 from stu join score on stu.id = score.stuId join department on stu.departmentId = department.id where department.`name` = '数学学院' GROUP BY stu.id having 总分 > ( select sum(score.score) from stu join score on stu.id = score.stuId join department on stu.departmentId = department.id where department.`name` = '计算机学院' GROUP BY stu.id ORDER BY sum(score.score) desc limit 1 );
3.2 视图的使用
3.2.1 创建视图
use yggl;
-
在
YGGL数据库创建视图ds_view，视图包含Departments表的全部列。CREATE OR REPLACE VIEW `yggl`.`ds_view` AS SELECT * FROM departments; -
在
YGGL数据库创建视图Employees_view，视图包含员工号码、姓名和实际收入。CREATE OR REPLACE VIEW `yggl`.`Employees_view` AS SELECT employees.EmployeeID, employees.`Name`, salary.InCome - salary.OutCome as 实际收入 FROM employees INNER JOIN salary ON employees.EmployeeID = salary.EmployeeID; -
创建视图，包含员工号码、姓名、所在部门名称和实际收入列。
CREATE VIEW `yggl`.`创建视图` AS SELECT employees.EmployeeID, employees.`Name`, departments.DepartmentName, salary.InCome - salary.OutCome as 实际收入 FROM employees INNER JOIN departments ON employees.DepartmentID = departments.DepartmentID INNER JOIN salary ON employees.EmployeeID = salary.EmployeeID;
3.2.2 查询视图
-
从视图
ds_view中查询出部门号为3的部门名称。select DepartmentName from ds_view where DepartmentID = 3; -
从视图
Employees_view中查询出姓名为“王林”的员工的实际收入。select 实际收入 from employees_view where `Name` = '王林';
3.2.3 更新视图
-
向视图
ds_view中插入一行数据：6，财务部，财务管理。insert into ds_view values('6', '财务部', '财务管理'); -
尝试向视图
Employees_view中插入一行数据，看看会发生什么。
insert into Employees_view values('100000', '邓文辉', '9999');会报错，错误如下： > 1394 - Can not insert into join view 'yggl.employees_view' without fields list 原因是不能修改联合视图！ -
修改视图
ds_view，将部门号为5的部门名称修改为“生产车间”。update ds_view set DepartmentName = '生产车间' where DepartmentID = '5'; -
修改视图
Employees_view中号码为“000001”的员工的姓名为“王浩”。update employees_view set `Name` = '王浩' where EmployeeID = '000001'; -
删除视图
ds_view中部门号为“1”的数据。delete from ds_view where DepartmentID = '1';
3.2.4 删除视图
- 删除视图
ds_view。# 删除视图 ds_view drop view if exists ds_view;
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