3 案例答案

3.1 第二章

3.1.1 案例1

案例

设计一张员工信息表，要求如下： 1. 编号（纯数字）2. 员工工号 (字符串类型，长度不超过10位) 3. 员工姓名（字符串类型，长度不超过10位） 4. 性别（男/女，存储一个汉字） 5. 年龄（正常人年龄，不可能存储负数） 6. 身份证号（二代身份证号均为18位，身份证中有X这样的字符） 7. 入职时间（取值年月日即可）

对应的建表语句如下:

create table emp(
    id int comment '编号',
    workno varchar(10)  comment '工号',
    name varchar(10) comment '姓名',
    gender char(1) comment '性别',
    age tinyint unsigned comment '年龄',
    idcard char(18) comment '身份证号',
    entrydate date comment '入职时间'
) comment '员工表';

desc emp

3.1.2 数据2

drop table if exists employee;

create table emp(
    id int comment '编号',
    workno varchar(10) comment '工号',
    name varchar(10) comment '姓名',
    gender char(1) comment '性别',
    age tinyint unsigned comment '年龄',
    idcard char(18) comment '身份证号',
    workaddress varchar(50) comment '工作地址',
    entrydate date comment '入职时间'
)comment '员工表';

INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (1, '00001', '柳岩666', '女', 20, '123456789012345678', '北京', '2000-01-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (2, '00002', '张无忌', '男', 18, '123456789012345670', '北京', '2005-09-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (3, '00003', '韦一笑', '男', 38, '123456789712345670', '上海', '2005-08-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (4, '00004', '赵敏', '女', 18, '123456757123845670', '北京', '2009-12-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (5, '00005', '小昭', '女', 16, '123456769012345678', '上海', '2007-07-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (6, '00006', '杨逍', '男', 28, '12345678931234567X', '北京', '2006-01-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (7, '00007', '范瑶', '男', 40, '123456789212345670', '北京', '2005-05-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (8, '00008', '黛绮丝', '女', 38, '123456157123645670', '天津', '2015-05-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (9, '00009', '范凉凉', '女', 45, '123156789012345678', '北京', '2010-04-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (10, '00010', '陈友谅', '男', 53, '123456789012345670', '上海', '2011-01-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (11, '00011', '张士诚', '男', 55, '123567897123465670', '江苏', '2015-05-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (12, '00012', '常遇春', '男', 32, '123446757152345670', '北京', '2004-02-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (13, '00013', '张三丰', '男', 88, '123656789012345678', '江苏', '2020-11-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (14, '00014', '灭绝', '女', 65, '123456719012345670', '西安', '2019-05-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (15, '00015', '胡青牛', '男', 70, '12345674971234567X', '西安', '2018-04-01');
INSERT INTO emp (id, workno, name, gender, age, idcard, workaddress, entrydate) VALUES (16, '00016', '周芷若', '女', 18, null, '北京', '2012-06-01');

3.1.3 案例3

在emp数据表中：

-- 1. 查询年龄为20,21,22,23岁的员工信息。
SELECT * FROM emp WHERE age IN(20,21,22,23);
SELECT * FROM emp WHERE age BETWEEN 20 AND 23;
-- 2. 查询性别为 男 ，并且年龄在 20-40 岁(含)以内的姓名为三个字的员工。
SELECT * FROM emp WHERE gender = '男' AND age BETWEEN 20 AND 40 AND `name` LIKE '___';
-- 3. 统计员工表中, 年龄小于60岁的 , 男性员工和女性员工的人数。
SELECT gender, COUNT(*) FROM emp WHERE age<60 GROUP BY gender; 
-- 4. 查询所有年龄小于等于35岁员工的姓名和年龄，并对查询结果按年龄升序排序，如果年龄相同按入职时间降序排序。
SELECT `name`, age FROM emp WHERE age<=35 ORDER BY age ASC, entrydate DESC;
-- 5. 查询性别为男，且年龄在20-40 岁(含)以内的前5个员工信息，对查询的结果按年龄升序排序，年龄相同按入职时间升序排序。
SELECT * FROM emp WHERE gender='男' AND age BETWEEN 20 AND 40 ORDER BY age ASC, entrydate ASC LIMIT 5;