0. scott 用戶默認表介紹

scott用戶Tables目錄下包含四張表

1. insert（插入）語句

給指定列插入數據：

insert into dept(deptno,dname) values(50,‘xx‘);

插入全部列數據：

insert into dept(deptno,dname,loc) values(60,‘xx‘,‘lll‘);

2. update（更新）語句

update dept set dname=‘司法部‘ where deptno=50;
update dept set dname=‘司法部‘ ,loc=
 
‘china‘ where deptno=50;

3. delete（刪除）語句

刪除指定數據：

delete from dept where deptno=70;

刪除指定條件的數據：

delete from dept where deptno>40;

4. select（查詢）語句

查詢所有：

select * from emp;

指定字段查詢：

select ename,sal from emp;

簡寫

insert into dept values(70,‘xxx‘,‘llll‘);

加 where 條件：

select * from emp where sal>=800;
select * from emp where sal>=1500 and job=‘SALESMAN‘;

Distinct 去重復記錄；

Group by 分組查詢：select job,count(ename) as num from EMP t group by job;

Having 過濾分組：select job,count(ename) as num from EMP t group by job having count(ename)>=2;

Order by 排序：select * from emp order by sal desc;

子查詢：查詢出基本工資大於平均工資的員工：select * from emp where sal>(select avg(sal) from emp)

聯合查詢：

並集（去重復）：

select * from t_user1
union
select * from t_user2;

並集：

select * from t_user1
union all
select * from t_user2;

交集：

select * from t_user1
intersect
select * from t_user2;

差集：

select * from t_user1
minus
select * from t_user2;

內連接：

select * from emp t,dept d where t.deptno=d.deptno;

類似：select * from emp e inner join dept d on e.deptno=d.deptno; inner 可以省略；

外連接：

左外連接：select * from emp e left join dept d on e.deptno=d.deptno;

右外連接：select * from emp e right join dept d on e.deptno=d.deptno;

（三）Oracle學習筆記—— sql語句