In this lesson we are going to study about Non Equi joins in a database.
Non Equi Join:
Table aliases used for reduce the code length and as well as the execution time .
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Non Equi Join:
Non eque join is a type of join in which we can join two table with the join condition where the join condition uses other than equal operator “=”.
Example: In the below diagram we are having two table EMPLOYEES and JOB_GRADES.
EMPLOYEES tabel contain the lastname and salary of the employee and JOB_GRADE contain the grading (Gra),lowest salary and highest salary.
A relation between the two table is that the salary columns in the EMPLOYEES table must be between the values in the Lowest_sal and Highest_sal columns of the JOB_GRADES table.The relationship is obtained using an operator other than equal(=).
Non Equi join Sample:
select e.last_name,e.salary,j.gra
from employees e,job_grades j
where e.salary between j.lowest_sal and j.highest_sal
NOTE: Other condition ,such as <= and >= can be used ,but BETWEEN is the simplest .Remember specify the low value first and hight value last when useing BETWEEN.Table aliases used for reduce the code length and as well as the execution time .
Related Article
- Join
- Cross Join
- Equi Join
- Self Join
- Natural Join
- Join with Using clause.
- Join with ON clause
- Outer Join.
