Oracle

In database , Filtering is important. We use some keyword to filter data.

DISTINCT

DISTINCT clause is used to remove the duplicate records from the result set.

It is only used with SELECT statement.

Syntax:

SELECT DISTINCT expressions  
FROM tables  
WHERE conditions;  

Example:

select distinct sname
from students
where student_city = 'Delhi';

WHERE

The WHERE clause specifies a search condition for rows returned by the SELECT statement.

syntax:

SELECT  select_list
 FROM   table_name 
WHERE   search_condition;

Example:

select *
from students
where student_city = 'Delhi';

AND

It combine two or more Boolean expressions and return true if all expressions are true.

syntax:

expression_1 AND expression_2

Example:

select *
from students
where student_city = 'Delhi' and student_type ='Day Scholar';

OR

It combine two or more Boolean expressions and return true if one of the expressions is true.

syntax:

expression_1 OR expression_2

Example:

select *
from students
where student_city = 'Delhi' or student_type ='Day Scholar';

BETWEEN

It is used filter data based on a range of values.

syntax:

value_1 BETWEEN value_2

Example:

select *
from students
where student_id between 2104 and 2107;

LIKE

Sometimes, you want to query data based on a specified pattern. For example, you may want to find contacts whose last names start with 'St' or first names end with 'er'. In this case, you use the Oracle LIKE operator.

syntax:

LIKE = 'specific pattern'

Example:

NULL / NOT NULL

check if an expression or values in a column is NULL or not.

syntax:

expression |  column  IS NULL | NOT NULL