PHP quick introduction to SQL statements

2020-05-09 19:29:30
OfStack
                    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; 

|, | concatenation and addition, subtraction, multiplication, and division and the use of parentheses

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

2 from employees; 

+- USES the plus and minus sign

SQL
>
 select -salary from employees; 

<

>
,
>
,
<
, =,! = equal comparison operator

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(more than any other)

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

some is an equivalent of SQL-92 standard any

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

all (more than all)

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; 

Logical operator

And and 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; 

The dual dummy table can be used when there is no table to query

select sysdate from dual; 

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