One of the most basic yet essential operations we can perform on data is to put it in order. Imagine how useless a phone book would be if the names appeared in random order. One of the most valuable features of a relational database is the flexibility it allows us in sorting our data.
To sort the data returned from a SELECT statement, we add an ORDER BY clause at the end of the other options we've seen so far. This is the basic format:
SELECT select_list FROM table_list [WHERE condition] [GROUP BY clause] ORDER BY order_list
The order_list is similar to the select list: It is a list of column names or expressions containing column names that are used in decreasing order of priority in determining the sort order.
For example, ...