Oracle學習筆記（一） 簡單查詢

001:在sql語句中使用算術運算子

select empno, ename, (500+sal)*12 

from emp;

select empno as "員工編號", ename name, (500+sal)*12 "annual salary" 

from emp;

如果在別名中包含了特殊字元(如中文字元), 或想讓別名原樣顯示, 就要用雙引號把別名擴起來.

003:連線運算子

select ename || ' annual salary is ' || (500+sal)*12 "employee's salary" 

from emp;
select ename || '的年薪為:' || (500+sal)*12 "員工的年薪" 
from emp;

select distinct deptno 

from dept;
select distinct deptno,job 
from emp;

005:選擇性查詢

--選擇性查詢

select empno, ename, sal 
from emp 
where sal>=1500;
--between運算子用於數字
select empno, ename, sal 
from emp 
where sal between 1500 and 2900;
--between運算子用於日期
select empno, ename, sal, hiredate
from emp
where hiredate between '01-jan-81' and '31-may-82';
--not between運算子用於日期
select empno, ename, sal, hiredate
from emp
where hiredate not between '01-jan-81' and '31-may-82';
--"="運算子
select empno, ename, job
from emp
where job='salesman';
--in運算子
select empno, ename, sal, job
from emp
where job in('salesman', 'clerk', 'manager');
--not in運算子 
select empno, ename, sal, job
from emp
where job not in('analyst', 'president'); 
--like比較運算子, %萬用字元
select empno, ename, sal, job 
from emp 
where job like 'sal%';
--like比較運算子, _萬用字元
select empno, ename, sal, job
from emp 
where job like 's_l_s%';
--like比較運算子, %萬用字元用於日期
select empno, ename, sal, hiredate 
from emp
where hiredate like '%81';

--建立臨時表單

create table dept_temp 
as select * from dept; 
--在表單內加入測試項
insert into dept_temp 
values(88, 'it_research', 'beijing');
--使用轉義操作符
select * 
from dept_temp 
where dname like 'it\_%' escape'\';

--增序(預設情況)

select empno, ename, sal 
from emp 
where sal >= 1500 
order by sal asc;
--降序
select empno, ename, sal 
from emp 
where sal >= 1500 
order by sal desc; 
--在order by 子句中使用別名 
select empno as "employee number", ename name, (500+sal)*12 "annual salary" 
from emp 
order by "annual salary" desc;
--在order by 子句中使用表示式
select empno as "employee number", ename name, (500+sal)*12 "annual salary" 
from emp 
order by (500+sal)*12 desc;
--在order by 子句中使用列號
select empno as "employee number", ename name, (500+sal)*12 "annual salary" 
from emp 
order by 3 desc;
--在order by 子句中使用多列進行排序, 首先按job進行排序,然後按sal進行排序
select ename, job, sal 
from emp 
order by job, sal desc;
--使用不在select列表中的列來排序
select ename, job, sal 
from emp 
order by empno;

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