Before it is marked as a duplicate, I am not asking If I have to specify it fully, I am why it does not matter if it is specified. Hope that clears that up. Now to the question.
I'm new to SQL so I'm not sure if there is some technical term for this.
Say I have a database with tables: Orders and Customers.
Orders has categories: OrderID, CustomerID, and OrderDate
Customers has categories: CustomerID, CustomerName, ContactName, and Country
I then have a SQL Query:
SELECT Orders.OrderID, Customers.CustomerName, Orders.OrderDate
FROM Orders
INNER JOIN Customers ON Orders.CustomerID=Customers.CustomerID;
So I am selecting Orders.OrderID, Customers.CustomerName, and Orders.OrderDate FROM Orders table. If it is from the Orders table, why specify Orders. before the OrderID and OrderDate in select ? This is an example from a website, and does not explain this. I am not sure if it has to do with join (which is in the example) so that's why I also put it there and in the tags.
-Thanks
Sometimes the column name is found in both tables and your DBMS will throw an error that the column is ambiguous. It's usually a good idea to explicitly declare which table you want the item to come from.
Using an alias often make the code easier to read and write:
SELECT ord.OrderID, cus.CustomerName, ord.OrderDate
FROM Orders ord
INNER JOIN Customers cus ON ord.CustomerID=cus.CustomerID;
These table names are pretty short, but you can see how useful aliases can be when the table names become longer and more complicated.
One benefit to explicitly declaring the table is that you can tell at a glance what table the data is coming from. Once you have data coming from many sources, through joins or not, it can be difficult to tell exactly which table a field is coming from, if you do not show the table in the select statements.