第二章 Oracle過濾和排序數據

一、在查詢中過濾行(where)

select employee_id,last_name,salary
  from employees
  where employee_id  > 200

操作符	含義
=	等於（不是==）
>	大於
>=	大於、等於
<	小於
<=	小於、等於
<>	不等於（也可以是！=）

賦值使用：=符號

between…and…包含邊界值

select last_name,hire_date,salary
	from employees
	where salary>=4000 and salary<=7000;

select last_name,hire_date,salary
	from employees
	where salary between 4000 and 7000;

in取括號中的幾個值（離散值）

select last_name,hire_date,salary,department_id
	from employees
	where department_id =90 or department_id =80 or department_id=70

select last_name,hire_date,salary,department_id
	from employees
	where department_id in (70,80,90);

like模糊查詢

select last_name,hire_date,salary,department_id
	from employees
	where last_name like '%a%';
--like
--員工中名字含有字符a的員工

select last_name,hire_date,salary,department_id
	from employees
	where last_name like '%a';
--員工中名字末位是a的員工

select last_name,hire_date,salary,department_id
	from employees
	where last_name like '%\_%' escape '\';
--員工中名字含有_的員工

null 空

select last_name,hire_date,salary,department_id,commission_pct
	from employees
	where commission_pct is null;

1.邏輯運算

操作符	含義
AND	邏輯並
OR	邏輯或
NOT	邏輯否

select last_name,hire_date,salary,department_id,commission_pct
	from employees
	where department_id = 80 and salary <=8000;

2.優先級

優先級
1	算法運算符
2	連接符
3	比較符
4	IS (NOT) NULL,LIKE,(NOT) IN
5	(NOT) BETWEEN
6	NOT
7	AND
8	OR

可以使用括號改變優先級順序

二、在查詢中對行進行排序

select last_name,hire_date,salary,department_id,commission_pct
from employees
	where department_id = 80 
	order by salary desc
--desc降序 asc升序，默認爲desc

select last_name,hire_date,salary,department_id,commission_pct
	from employees
	where department_id = 80 
	order by salary asc，last_name asc;
--根據工資降序排序，工資相同時按照工資排序

總結

1.使用where子句過濾數據

• 使用比較運算
• 使用between and，in，like，null運算
• 使用邏輯運算符AND,OR和NOT

2.使用ORDER BY子句進行排序