SQL语句快速入门

 

Select * from tablename

SQL> select * from employees;

Select select list from tablename

SQL> select employee_id,first_name from employees;

Select distinct … from tablename

SQL> select distinct manager_id from employees;

||连接符使用以及 加减乘除以及括号的使用

SQL> select employee_id,first_name||'.'||last_name,salary*(1+0.1)/100,manager_id

  2  from employees;

+-做正负号使用

SQL> select  -salary  from employees;

<>,>,<,=,!=等比较操作符

SQL> select  *  from employees where salary >13000;

SQL> select  *  from employees where salary <13000;

SQL> select  *  from employees where salary <>13000;

SQL> select  *  from employees where salary =13000;

In

SQL> select  -salary  from employees where employee_id in (100,101,102);

SQL> select  -salary  from employees where employee_id in (select employee_id from  employees);

not in

SQL> select  -salary  from employees where employee_id not in (100,101,102);

Any(比任意一个都)

select *  from employees where employee_id >any(100,101,102);

some 是 SQL-92 标准的 any 的等效物

select *  from employees where employee_id >any(100,101,102);

all（比所有的都）

select *  from employees where employee_id >all(100,101,102);

between and

select *  from employees where employee_id  between 100 and 102;

not between and

select *  from employees where  employee_id not between 100 and 102;

逻辑操作符

And 和 or

select *  from employees where  employee_id > 100 and   employee_id < 1000;

select *  from employees where  employee_id > 100 or   employee_id < 1000;

Order by

Desc

select *  from employees where employee_id  between 100 and 102 order by employee_id desc;

Asc

select *  from employees where employee_id  between 100 and 102  order by employee_id asc;

dual哑元表没有表需要查询的时候可以用它

select sysdate from dual;

select 1*2*3*4*5 from dual;