Select statement with WHERE clause

WHERE Clause in SELECT Statement.

                                                        The where clause in SELECT statement is used to filter out records in table according to user constrains. It also used merge two or more by join statement. 

SELECT with WHERE

      SELECT Column-Names FROM table_name WHERE (Condition);

condition may be any 

• Relational Condition =, <, >, !=  
• Logical Condition AND, OR and NOT 
• Special Operator IN, BETWEEN, ANY, ALL, SOME, EXISTS.

Example table and Statement.

Employee

id	Emp_name	Age	Salary
1	Jebas	35	40,000
2	Thomas	30	80,000
3	Mark	25	40,000
4	Harry	42	50,000
5	Willam	45	100,000

        SELECT Id,Emp_name FROM Employee Where id=1;  

This statement return Emp_name with row of  table  condition satisfying id =1     

 

id	Emp_name
1	Jebas

        SELECT Emp_name, Salary FROM Employee Where Salary=40,000;

This statement  return Emp_name and Salary of Employee with row of table value condition satisfying salary equal to 40,000.

id	Emp_name	Salary
1	Jebas	40,000
3	Mark	40,000

SELECT Statement with Logical Condition Operator.

SQL using AND

         SELECT Emp_name ,Age, Salary FROM Employee Where Age>40 AND Salary>40,000;   

This statement return Employee Name, Age, Salary with condition satisfying age greater than 40 and salary greater than 40,000.  

Emp_name	Age	Salary
Harry	42	50,000
Willam	45	100,000

    

SQL using OR

         SELECT Emp_name ,Age, Salary FROM Employee  Where Age>40 OR Salary=40,000;

This statement return Employee Name, Age, Salary with condition satisfying either age greater than 40 or salary greater than 40,000. 

Emp_name	Age	Salary
Jebas	35	40,000
Mark	25	40,000
Harry	42	50,000
Willam	45	100,000

SQL using NOT

        SELECT Emp_name FROM Employee Where Salary NOT > 35;

This statement return Employee Name with condition satisfying salary not greater than 35.

Emp_name

Mark

Thomas

SELECT Statement with Special Operator.

SQL using IN 

        SELECT Emp_name FROM Employee WHERE Age IN(25,35);

This statement return Employee Name , whose age are in 25 and 35.

This statement can also written as

       SELECT Emp_name FROM Employee WHERE Age = 25 or Age=35;

Emp_name

Jebas

Mark

SQL Using Between

          SELECT Emp_name,Age FROM Employee WHERE Age Between 25 and 40;

This statement return Emp_name where Employee age between 25 and 40.

Emp_name	Age
Jebas	35
Thomas	30
Mark	25

 This statement can also written as 

SELECT Emp_name,Age FROM Employee WHERE Age > 25 and Age<= 40;

ANY, ALL, SOME, EXISTS Keyword are used with SUBQUERY will see in https://www.followlect.com/2020/06/any-all-exists-operators-in-sql-query.html post.

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