SQL INNER JOIN

Hello Friends, welcome again, in this post I will discuss about the SQL INNER JOIN, from the last post we already know the use of JOIN, basically to join two tables in a Database based on Primary Key.

So, lets look at our table and then query for INNER JOIN


Table1: Customer

CID     Name         Designation
222      Whiskey       Moderator
444      Onty             Member
111      Gaurav         Admin
333      Kumaar       Admin
555      Rishabh       Admin
666      Rose           Admin
888      White          Member
999      Mikey         Member


Table2: Orders

OID    Product        CID
1          Perfume        666
2          Laptop         444
3          Perfume        999
4          Cell Phone    666

Syntax:
SELECT column_name(s)
FROM table1
INNER JOIN table2
ON table1.column_name = table2.column_name
ORDER BY column_name

ORDER BY is optional.

Now For our Query:

SELECT Customer.Name, Orders.Product
FROM Customer
INNER JOIN Orders
ON Customer.CID = Orders.CIDORDER BY Customer.Name

Note: Customer.Name and Customer.Designation means, select the Name and Designation Columns from Customer Table, same for the Orders Table.

Our Result set will have:

Name    Products
Mikey     Perfume
Onty       Laptop
Rose       Perfume
Rose      Cell Phone

Explanation: In simple words just think that SQL will start checking the Customer.CID with each records of Orders.CID, in case it finds a match, it would extract it to the result-set, and look for next until no records found. Example: SQL will start with Customer.CID(222) and check each records on the Orders Table in the Orders.CID column, if there are any records that matches the values, it would show in the result set, since we have added an ORDER BY on Customer.Name, it would sort the display on the Customer.Name Column. Once its done with 222, it would move to next, that is 444, and perform the same function.

Its little confusing I know, but hang around here try with own examples, and I am sure you can get around the logic of this.

Hope this was informative, and Don't Forget to check the next Post.

Thank You!