数据库学习笔记——DML

建表：

CREATE TABLE employee(employee_ID int not null,employee_name varchar(20) not null,street varchar(20) not null,city varchar(20) not null,PRIMARY KEY(employee_ID)
);CREATE TABLE company(company_name varchar(30) not null,city varchar(20) not null,PRIMARY KEY(company_name)
);create table manages(employee_ID int not null,manager_ID int,primary key(employee_ID),foreign key(employee_ID) references employee(employee_ID) on delete cascade,foreign key(manager_ID) references employee(employee_ID) on delete set null			
);create table works(employee_ID int not null,company_name varchar(30),salary numeric(8,2) check (salary>3000),  primary key(employee_ID),foreign key(employee_ID) references employee(employee_ID) on delete cascade,foreign key(company_name) references company(company_name) on delete set null									
);

将数据插入employee表：

INSERT into employee (employee_ID,employee_name,street,city) VALUES (319001,'Johnson','XihuRoad','Hangzhou');INSERT into employee (employee_ID,employee_name,street,city) VALUES (319002,'Glenn','XihuRoad','Hangzhou');INSERT into employee (employee_ID,employee_name,street,city) VALUES (319003,'Williams','ZhongshanRoad','Wuhan');INSERT into employee (employee_ID,employee_name,street,city) VALUES (319004,'Chambers','Jiefang Road','Maoming');INSERT into employee (employee_ID,employee_name,street,city) VALUES (319005,'Brooks','Secong Road','Shenzhen');INSERT into employee (employee_ID,employee_name,street,city) VALUES (319006,'Greens','Xiyuan','GuangZhou');INSERT into employee (employee_ID,employee_name,street,city) VALUES (319007,'Turner','FirstRoad','Shenzhen');INSERT into employee (employee_ID,employee_name,street,city) VALUES (319008,'Wilder','FirstRoad','Shenzhen');INSERT into employee (employee_ID,employee_name,street,city) VALUES (319009,'FrieRice','Xiyuan','GuangZhou');INSERT into employee (employee_ID,employee_name,street,city) VALUES (319010,'Jackson','University','Tianjing');INSERT into employee (employee_ID,employee_name,street,city) VALUES (319011,'MrSmithen','Beijing Road','Wuhan');INSERT into employee (employee_ID,employee_name,street,city) VALUES (319012,'Majeris','First','Beijing');INSERT into employee (employee_ID,employee_name,street,city) VALUES (319013,'McBride','Safety','Beijing');INSERT into employee (employee_ID,employee_name,street,city) VALUES (319014,'Curry','North','Tianjing');INSERT into employee (employee_ID,employee_name,street,city) VALUES (319015,'Edmonds','University','Tianjing');INSERT into employee (employee_ID,employee_name,street,city) VALUES (319016,'Smith','Beijing Road','GuangZhou');INSERT into employee (employee_ID,employee_name,street,city) VALUES (319017,'Shelby','Beijing Road','GuangZhou');INSERT into employee (employee_ID,employee_name,street,city) VALUES (319018,'MrChen','First','Foshan');INSERT into employee (employee_ID,employee_name,street,city) VALUES (319019,'McDong','Safety','Maoming');INSERT into employee (employee_ID,employee_name,street,city) VALUES (319020,'MrDeng','FirstRoad','Shenzhen');INSERT into employee (employee_ID,employee_name,street,city) VALUES (319021,'DongXin','FirstRoad','Shenzhen');INSERT into employee (employee_ID,employee_name,street,city) VALUES (319022,'CbingQuan','Jiefang Road','Maoming');INSERT into employee (employee_ID,employee_name,street,city) VALUES (319023,'Leach','SecondRoad','Shenzhen');

将数据插入company表：

INSERT into company (company_name,city) VALUES ('Alibaba','Hangzhou');INSERT into company (company_name,city) VALUES ('Baidu','Beijing');INSERT into company (company_name,city) VALUES ('Huawei','Shenzhen');INSERT into company (company_name,city) VALUES ('Netease','GuangZhou');INSERT into company (company_name,city) VALUES ('Tensent','Shenzhen');INSERT into company (company_name,city) VALUES ('The People Bank','Beijing');

将数据插入manages表：

INSERT into manages (employee_ID,manager_ID) VALUES (319005,NULL);INSERT into manages (employee_ID,manager_ID) VALUES (319001,319002);INSERT into manages (employee_ID,manager_ID) VALUES (319003,319002);INSERT into manages (employee_ID,manager_ID) VALUES (319002,319004);INSERT into manages (employee_ID,manager_ID) VALUES (319004,319004);INSERT into manages (employee_ID,manager_ID) VALUES (319006,319005);INSERT into manages (employee_ID,manager_ID) VALUES (319007,319005);INSERT into manages (employee_ID,manager_ID) VALUES (319008,319005);INSERT into manages (employee_ID,manager_ID) VALUES (319010,319009);INSERT into manages (employee_ID,manager_ID) VALUES (319016,319009);INSERT into manages (employee_ID,manager_ID) VALUES (319012,319014);INSERT into manages (employee_ID,manager_ID) VALUES (319013,319014);INSERT into manages (employee_ID,manager_ID) VALUES (319014,319014);INSERT into manages (employee_ID,manager_ID) VALUES (319009,319017);INSERT into manages (employee_ID,manager_ID) VALUES (319017,319017);INSERT into manages (employee_ID,manager_ID) VALUES (319018,319018);INSERT into manages (employee_ID,manager_ID) VALUES (319019,319018);INSERT into manages (employee_ID,manager_ID) VALUES (319020,319021);INSERT into manages (employee_ID,manager_ID) VALUES (319021,319021);INSERT into manages (employee_ID,manager_ID) VALUES (319022,319021);INSERT into manages (employee_ID,manager_ID) VALUES (319023,319021);

将数据插入works表：

INSERT into works (employee_ID,company_name,salary) VALUES (319001,'Alibaba',7633.00);INSERT into works (employee_ID,company_name,salary) VALUES (319002,'Alibaba',12500.00);INSERT into works (employee_ID,company_name,salary) VALUES (319003,'Alibaba',10500.00);INSERT into works (employee_ID,company_name,salary) VALUES (319004,'Alibaba',17000.00);INSERT into works (employee_ID,company_name,salary) VALUES (319005,'Tensent',15000.00);INSERT into works (employee_ID,company_name,salary) VALUES (319006,'Tensent',10500.00);INSERT into works (employee_ID,company_name,salary) VALUES (319007,'Tensent',10655.00);INSERT into works (employee_ID,company_name,salary) VALUES (319008,'Tensent',12000.00);INSERT into works (employee_ID,company_name,salary) VALUES (319009,'Baidu',20000.00);INSERT into works (employee_ID,company_name,salary) VALUES (319010,'Baidu',19000.00);INSERT into works (employee_ID,company_name,salary) VALUES (319011,'Netease',8000.00);INSERT into works (employee_ID,company_name,salary) VALUES (319012,'The People Bank',7000.00);INSERT into works (employee_ID,company_name,salary) VALUES (319013,'The People Bank',6335.00);INSERT into works (employee_ID,company_name,salary) VALUES (319014,'The People Bank',18500.00);INSERT into works (employee_ID,company_name,salary) VALUES (319015,'The People Bank',19000.00);INSERT into works (employee_ID,company_name,salary) VALUES (319016,'Baidu',18000.00);INSERT into works (employee_ID,company_name,salary) VALUES (319017,'Baidu',21000.00);INSERT into works (employee_ID,company_name,salary) VALUES (319018,'Netease',15000.00);INSERT into works (employee_ID,company_name,salary) VALUES (319019,'Netease',8000.00);INSERT into works (employee_ID,company_name,salary) VALUES (319020,'Huawei',13000.00);INSERT into works (employee_ID,company_name,salary) VALUES (319021,'Huawei',16000.00);INSERT into works (employee_ID,company_name,salary) VALUES (319022,'Huawei',14000.00);INSERT into works (employee_ID,company_name,salary) VALUES (319023,'Huawei',15000.00);

创建临时数据表temp1，其中字段x、y、z数据类型依次为FLOAT(5,1)、DOUBLE(5,1)和DECIMAL(5,1), 向表中插入数据5.12、5.15和5.123 :

CREATE TABLE temp1(x FLOAT(5,1),y DOUBLE(5,1),z DECIMAL(5,1)
);INSERT into temp1 (x,y,z) VALUES (5.12,5.15,5.123);

出现警告信息：Data truncated for column ‘z’ at row 1

在创建一个decimal(5,1)的字段时，我们指定字段的总长度为5，小数点之后的位数为1，这意味着我们可以插入一个包含4个整数和1个小数点的数字。如果我们尝试插入超过该值的数据，z 的数据被截断，MySQL就会抛出上述异常。

创建临时数据表temp2, 定义数据类型为YEAR的字段 y，向表中插入值2010、‘2010’和‘2166’，并查看表temp2的结果 :

CREATE TABLE temp2(y YEAR
);INSERT into temp2 VALUES (2010);INSERT into temp2 VALUES ('2010');INSERT into temp2 VALUES ('2166');
# Out of range value for column 'y' at row 1

YEAR类型用于表示年份，使用4位字符串或数字表示，
范围为：‘1901’—‘2155’或1901—2155 。

向temp2表中的y字段插入2位字符表示的YEAR值，分别为‘0’，‘00’，‘77’和‘10’，并查看表temp2的结果：

drop TABLE temp2;CREATE TABLE temp2(y YEAR
);INSERT into temp2 VALUES ('0');INSERT into temp2 VALUES ('00');INSERT into temp2 VALUES ('77');INSERT into temp2 VALUES ('10');

使用两位字符串表示，范围为 ’00’—‘99’。其中， ’00’—‘69’ 范围的值会被转换为2000—2069范围的YEAR值；’70’—‘99’范围的值会被转换为1970—1999范围的YEAR 值。

向temp2表中的y字段插入2位数字表示的YEAR值，分别为0、78和11，并查看表temp2的结果：

drop TABLE temp2;CREATE TABLE temp2(y YEAR
);INSERT into temp2 VALUES (0);INSERT into temp2 VALUES (78);INSERT into temp2 VALUES (11);

使用两位数字表示，范围为1—99。

其中，1—69范围的值会被转换为2001—2069范围的YEAR值；

70—99范围的值会被转换为1970—1999范围的YEAR值。

注意：当使用YEAR类型时，一定要区分’0’和0。

因为字符串格式的’0’表示的YEAR值是2000而数字格式的0表示的YEAR值是0000。

创建临时表temp3，定义数据类型为TIME的字段t，向表中插入值‘10:05:05’、‘23:23’、‘2 10:10’、‘3 02’、‘10’，并查看表temp2的结果 :

CREATE TABLE temp3(t time
);INSERT INTO temp3 VALUES ('10:05:05');INSERT INTO temp3 VALUES ('23:23');INSERT INTO temp3 VALUES ('2 10:10');INSERT INTO temp3 VALUES ('3 02');INSERT INTO temp3 VALUES ('10');

‘D HH:MM:SS’格式的字符串：

D表示天数，取值范围是0~34。保存时，小时的值等于（D*24+HH）。

输入时可以是‘HH:MM:SS’,‘HH:MM’,‘D HH:MM’,‘D HH’,‘SS’等形式。

向temp3中插入值‘101112’、111213，0，‘107010’：

drop table temp3;CREATE TABLE temp3(t time
);INSERT INTO temp3 VALUES ('101112');INSERT INTO temp3 VALUES ('111213');INSERT INTO temp3 VALUES ('0');INSERT INTO temp3 VALUES ('107010');
# Incorrect time value: '107010' for column 't' at row 1

‘HHMMSS’格式的字符串或HHMMSS格式的数值表示：

例如，输入‘101112’，Time类型会转换成10：11：12；输入101112，Time类型会转换成10：11：12。

如果输入0或者‘0’，那么TIME类型会转换为00：00：00。

向temp3表中插入系统的当前时间：

INSERT INTO temp3 VALUES (CURRENT_TIME);

创建临时表temp4，定义数据类型为DATA的字段d，向表中插入‘1998-08-08’、‘19980808’和‘20201010’：

CREATE TABLE temp4(d DATE
);INSERT into temp4 VALUES ('1998-08-08');INSERT into temp4 VALUES ('19980808');INSERT into temp4 VALUES ('20201010');

修改姓名为‘Brooks’的工资为16000：

UPDATE works 
set salary=16000 
where employee_ID in (SELECT employee_ID from employee where employee_name='Brooks');

将‘Brooks’的公司改为‘Huawei’，工作改为‘17000’ :

UPDATE works
set company_name='Huawei',salary=17000
where employee_ID in (SELECT employee_ID from employee where employee_name='Brooks'); 

为所有雇员增加100元工资：

UPDATE works
set salary=salary+100;

删除姓名为“DongXin”雇员的信息：

DELETE from employee where employee_name='DongXin';