When joining tables in SQL, we often use aliases to shorten table names. Consider this query joining order lines (details) with orders inside the database:
[source:sql]SELECT O.OrderID, FirstName, LastName, ItemName, Quantity
FROM Orders O
INNER JOIN OrderDetails OD
ON O.OrderID = OD.OrderID;
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The above may work, but behind the scenes the database’s query analyzer has to associate each of the selected columns with their respective tables. Although this is a fast process, it can be skipped entirely by simply fleshing out the query like this:
[source:sql]SELECT O.OrderID, O.FirstName, O.LastName, OD.ItemName, OD.Quantity
FROM Orders O
INNER JOIN OrderDetails OD
ON O.OrderID = OD.OrderID;
[/source]