Oracle DML SQL語句總結

desc dept;--描述這張表

DML = Data Manipulation Language 數據操縱語言

insert into dept values (50, 'game', 'bj');
rollback;

備份表

create table emp2 as select * from emp;
create table dept2 as select * from dept;
create table salgrade2 as select * from salgrade;
create table emp3 as select * from emp;

insert

insert into dept2 values (50, 'game', 'bj');
insert into dept2 (deptno,dname) values (60, 'game2');
insert into dept2 select * from dept;--結構一樣

rownum

select empno,ename from emp;
select empno,ename from emp where rownum < 5;
select empno,ename from emp where rownum <= 5;


--ronum只能與<和<=連用，不能與>和=連用
select empno,ename from emp where rownum > 10;
select empno,ename from emp where rownum = 10;

select rownum r,ename from emp;
select ename from (select rownum r,ename from emp) where r > 10;

select ename,sal from emp order by sal desc;
select ename,sal from emp where rownum <=5 order by sal desc;

--求薪水最高的前5名僱員
select ename,sal from
  (select ename,sal from emp order by sal desc) where rownum <=5;

--薪水最高的第6到10名僱員（重點掌握），效率高BBS
select ename,sal from 
  (
    select ename,sal,rownum r from 
      (select ename,sal from emp order by sal desc)
)
where r >= 6 and r <=10;

update

update emp2 set sal = sal*2,ename=ename||'-' where deptno = 10;
select ename,sal from emp2 where deptno = 10;

delete

delete from emp2;
delete from dept2 where deptno < 25;