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表中数据的操作 – 删（delete）

1)删除特定的数据

 语法:delete from table_name where 条件;

  例子:删除mytest表中id为1001的数据

delete from mytest where id=1001;

2)删除所有的数据

 语法:delete from table_name;

  例子:删除mytest表中所有的数据

delete from mytest;

表中数据的操作 – 改（update）

1)更新特定的数据

语法:update table_name set f1=v1,f2=v2,...fn=vn
           where 条件;

例子:修改mytest表中id为1001的这条数据，将 姓名修改为aaa,年龄修改为50,生日修改为 2021-10-11。

update mytest set name='aaa',age=50,birthday='2021-10-11'
    where id=1001;

2）更改表中所有的数据

语法:update table_name set f1=v1,f2=v2,...fn=vn;

例子:修改mytest表中年龄为80，生日为2021-10-11

update mytest set age=80,birthday='2021-10-11';

创建下图的表格 t_employee 员工表 empno 员工编号 ename 员工姓名 job 职位 MGR 上级领导编号 Hiredate入职日期 sal 工资 comm 提成/绩效 deptno 部门号 t_dept 部门表 deptno 部门号 dname 部门名称 loc 部门所在地

use company;
drop table t_employee;
create table t_employee(
     empno int,
     ename varchar(20),
     job varchar(40),
     MGR int,
     Hiredate date,
     sal double(10,2),
     comm double(10,2),
     deptno int
);
insert into t_employee values
	(7369,'smith','clerk',7902,19810312,800.00,null,20),
	(7499,'allen','salesman',7698,19820312,1600.00,300,30),
	(7521,'ward','salesman',7698,19830312,1250.00,500,30),
	(7566,'jones','manager',7839,19810312,2975.00,null,20),
	(7654,'martin','salesman',7698,19810312,1250.00,1400,30),
	(7698,'blake','manager',7839,19810312,2850.00,null,30),
	(7782,'clark','manager',7839,19850312,2450.00,null,10),
	(7788,'scott','analyst',7566,19810312,3000.00,null,20),
	(7839,'king','president',null,19810312,5000.00,null,10),
	(7844,'turner','salesman',7698,19890312,1500.00,0.00,30),
	(7876,'adams','clerk',7788,19980312,1100.00,null,20),
	(7900,'james','clerk',7698,19970312,950.00,null,30),
	(7902,'ford','analyst',7566,00000000,3000.00,null,20),
	(7934,'miller','clerk',7782,19810312,1300.00,null,10);

查看表结构 desc t_employee;

查看表内容 select * from t_employee;

drop table t_dept;
create table t_dept(
   deptno int,
   dname varchar(20),
   loc varchar(20)
);
insert into t_dept values(10,'accounting','newyork');
insert into t_dept values(20,'research','dallas');
insert into t_dept values(30,'sales','chicago');
insert into t_dept values(40,'operations','boston');
select * from t_dept;