Join in RDBMS
Use of Join in RDBMS
I am working as freelancer. I am a experienced full stack web developer. My lovely stack is MERN but I am open for new tech. I love to work with teammates for achieve goals. I love researches to find specific new things.
We have discussed in the previous blog how to normalize a table in DBMS because without normalization a table is very complex to process structured data.
What is Join?
Let's see some tables of an e-commerce company like Flipkart, amazon etc.
Suppose it has records stored in the following tables.
In this company, there are three tables of three different entity-Sales, Customer and Product.
A company always focuses on its sales. If this company wants a report of most purchased sales by the youth people, then a developer needs:
Youth people age's group data by--> Customer Table
Sales data by --> Sales Table
Hottest selling Product by--> Product Table
Thus, we have to keep a deep insight into different tables.
Join is a process to find data from different tables in a specific way. Join combines two different tables and gives user-according data or company-according data.
In further blogging, we will see joins wildly in SQL.
Types of Join
There are four categories of Join.
Inner Join
Left Join
Right Join
Full Join
Let's understand this before going deep study.
Inner Join
As seen in the ven diagram, Inner Join joins two left and right side tables and gives common data.
Right Join
Right join gives the right table's data and both the left and right table's joining data.
Left Join
As shown in this diagram, it gives the left table's data and both tables' common data.
Full Join
It takes everything present in both tables and also joins data(common data).
We will discuss more in further blog SQL.
