語法
select *|
from table
[where condition(s)];
示例
示例
select last_name, job_id, department_id
from employees
where last_name = 'whalen';
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!=)
示例
select last_name, salary
from employees
where salary <= 3000;
操作符
含義between…and…
在兩個值之間(包含邊界)
in(set)
等於值列表中的乙個
like
模糊查詢
is null空值
between
select last_name, salary
from employees
where salary between 2500
and3500;
in示例
select employee_id, last_name, salary, manager_id
from employees
where manager_id in (100, 101, 201);
like示例1
select first_name
from employees
where first_name like
's%';
示例2%
和-
可以同時使用
select last_name
from employees
where last_name like
'_o%';
示例3可以使用 escape 識別符號選擇『%』和 『_』 符號
迴避特殊符號的:使用轉義符。例如:將[%]轉為[\%]、[_]轉為[\_],然後再加上[escape 『\』] 即可
select job_id
from jobs
where job_id like 『it\_%『 escape 『\『;
示例
select last_name, manager_id
from employees
where manager_id is
null;
操作符
含義and
邏輯並or
邏輯或not
邏輯否
and
select employee_id, last_name, job_id, salary
from employees
where salary >=10000
and job_id like
'%man%';
orselect employee_id, last_name, job_id, salary
from employees
where salary >= 10000
or job_id like
'%man%';
notselect last_name, job_id
from employees
where job_id
notin ('it_prog', 'st_clerk', 'sa_rep');
優先順序
1算術運算子
2連線符
3比較符
4is[not]null,like,[not]in
5[not]between
6not
7and8or
可以使用括號改變優先順序順序
示例1
select last_name, job_id, department_id, hire_date
from employees
order
by hire_date ;
示例2降序排序
select last_name, job_id, department_id, hire_date
from employees
order
by hire_date desc ;
select employee_id, last_name, salary*12 annsal
from employees
order
by annsal;
示例
select last_name, department_id, salary
from employees
order
by department_id, salary desc;
對空值null的處理
優先順序排序
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