sql語句的練習

例：

create table department(

id int,
name varchar(50)
);

unian all是在顯示的時候將重複的資料剔除然後再顯示結果。

例：

select * from employee_chain union select * from employee_usa;

select e.id,e.name as '員工名',d.name as '部門' from employee e,department d where  e.depno = d.id  ;

select e.id,e.name as '員工名',d.name as '部門' from employee e inner join department d on e.depno = d.id  ;

左連線**：

select e.id,e.name as '員工名',d.name as '部門'  from employee e  left outer join department d on e.depno = d.id  ;

select e.id,e.name as '員工名',d.name as '部門'  from employee e  right outer join department d on e.depno = d.id 

新建兩個表
create  table depart(

depno int primary key,
name varchar(50),
location  varchar(50),
setuptime timestamp
);
create table emp(

empno int primary key,
ename varchar(50),
job varchar(50),
mgr int,
hiredate date,
sal decimal(7,2),
comm decimal(7,2),
depno int,
constraint fk_emp_depart foreign key(depno) references depart(depno)
);
constraint fk_emp_depart foreign key(depno) references depart(depno)

這句語句是指只能選擇選擇表depart裡的depno有的值。
子查詢**：
select * from emp where sal> (select sal from emp where ename='林同學' )
結果：

兩個表之中的聯絡：
select empno,sal,name,location from emp ,depart where emp.depno=depart.depno and emp.ename='劉同學';
				
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