After reading the question title you may find it silly but I'm seriously asking this question with curiosity in my mind.
I'm using MySQL database system.
Consider below the two tables :
Customers(CustomerID(Primary Key), CustomerName, ContactName, Address, City, PostalCode, Country)
Orders(OrderID(Primary Key), CustomerID(Foreign Key), EmployeeID, OrderDate, ShipperID)
Now I want to get the details of all orders that is which order is placed by which customer?
So, I did it in two ways :
First way:
SELECT o.OrderID, o.OrderDate, c.CustomerName
FROM Customers AS c, Orders AS o
WHERE c.CustomerID=o.CustomerID;
Second way:
SELECT Orders.OrderID, Orders.OrderDate, Customers.CustomerName
FROM Orders
INNER JOIN Customers ON Orders.CustomerID=Customers.CustomerID;
In both the cases I'm getting exactly the same correct result. My question is why there is a necessary of additional and confusing concept of Inner Join in MySQL as we can achieve the same results even without using Inner Join?
Is the Inner Join more effective in any manner?
What you are looking at is ANSI-89 syntax (A,B WHERE) vs ANSI-92 syntax (A JOIN B ON).
For very simple queries, there is no difference. However, there are a number of things you can do with ANSI-92 that you cannot do or that become very difficult to implement and maintain in ANSI-89. Anything more than two tables involved, more than one condition in the same join, or separating LEFT JOIN conditions from WHERE conditions are all much harder to read and work with in the older syntax.
The old A,B WHERE syntax is generally considered obsolete and avoided, even for the simple queries where it still works.