select EMPNO,SAL from emp where SAL BETWEEN 1000 and 2000--從enp中獲取sal中1000到2000之間的數據
select ENAME,SAL from emp where SAL >= 1000 and SAL <=2000--從enp中獲取sal中1000到2000之間的數據
select ENAME,SAL from emp where SAl IN(1000,2300);

select EMPNO from emp ORDER BY EMPNO;--默認排序
select EMPNO from emp ORDER BY EMPNO ASC--升序
select EMPNO from
 
 emp ORDER BY EMPNO DESC--降序

select LOWER( ENAME) from emp --大小寫的轉換

select * from emp;
                                                                                                                                                                                                                                                         

 
select * from emp;
select trim(ename) from emp--去掉首尾的空格

select * from emp;
select * from emp where ENAME = ‘KING‘--從中查找某個指定的

select * from emp;
select sal,sal+300 from emp--使用數學運算符“+”
select sal,sal*10 from emp--使用數學運算符“*”
select sal,10*sal+300 from emp--運算符的優先級
select sal,10*(sal+300)from emp--帶括好的運算

select
 
 * from emp;
select sal+20 AS sal_o from emp

select * from emp;
select ENAME || JOB from emp--連接符的運算
------數值函數-----

round--四舍五入
select round(412,-1) from dual--410
select round(412.777,2) from dual--412.78

trunc--截斷
select trunc(412.13,-1) from dual--410

MOD --求余
select MOd(200,11) from emp
select Mod(135.23,15) from dual

--日期函數
Months_between()---兩個日期相差的月數
select months_between(sysdate,hiredate) from emp
Last_day---本月的最後一天
select last_day(sysdate) from dual
Next_day()--指定日期的下個日期
select next_day(sysdate,‘星期一‘) from dual
-------------------------------------------------
select * from emp order by sal  DESC
select sal 
from emp 
order by sal DESC

--------------------------------------------------
Add_months()--向指定日期加上若幹月數
select Add_months(sysdate,0) from dual;


-----轉換函數----
to_char--對數字的轉換
select to_char(sysdate,‘yyyy‘) from dual;
select to_char(sysdate,‘fmyyyy-mm-dd‘) from dual;
select to_char(sal,‘L999,999,999‘) from emp;
select to_char(sysdate,‘D‘) from dual--返回星期

To_number--講字符轉換成數字
select to_number(‘13‘)+to_number(‘14‘) from dual---27

To_date
Select to_date(‘20090210‘,‘yyyyMMdd‘)from dual

------通用函數--
NVL()函數
select nvl(comm,1) from emp

-----------------------------------------------------------------
--模糊查詢like
select * from emp
select * from emp 
where job like ‘%*_%‘
-----邏輯運算符
--選擇在部門30中員工的所有信息
select * from emp 
where deptno=30;
--列出職位為（MANAGER）的員工的編號，姓名
select EMPNO,ENAME from emp 
where job=‘MANAGER‘
--找出獎金高於工資的員工
select *from emp 
where comm>sal
--找出每個員工獎金和工資的總和
select comm+sal,ename from emp
--找出部門10中的經理（MANAGER）和部門20中的普通員工（CLERK）
select * from emp
where (deptno=10 and job=‘MANAGER‘)or(deptno=20 and job=‘CLERK‘)
--找出部門10中既不是經理也不是普通員工，而且工資大於等於2000的員工
select *from emp
where deptno=10 and job not in(‘MANAGER‘,‘CLERK‘) and sal>=2000;
--找出有獎金的員工的不同工作
select distinct job from emp--distinct不同
where comm is not null and comm>0; 
--找出沒有獎金或獎金低於500的員工
select *from emp
where comm <500 or comm is null;
--顯示雇員信息姓名，根據其服務年限，將最老的雇員排在最前面
select ename from emp
order by hiredate;

SQL的基本語法練習