Column aliases exist to organizing output.In the previous example, whenever there is total sales, it is listed as SUM(sales). While this is understandable, we can have many cases where the column heading can be complicated (especially if it involves several arithmetic operations). Using a column alias its make the output much more readable.

Second is the table alias.This is accomplished by putting an alias directly after the table name in the FROM clause. This is convenient when you want to obtain information from two separate tables ('perform joins'). The advantage of using a table alias when doing joins is readily apparent when we talk about joins.

Both types of aliases are placed directly after the item they alias for, separate by a white space. We again use our table, Store_Information,

Notice that difference in the result that the column titles are now different. That is the result of using the column alias. Notice that instead of the somewhat cryptic "Sum(Sales)", we now have "Total Sales", which is much more understandable, as the column header. The advantage of using a table alias is not visible in this example. However, they will become evident in the Join Section