You would like to change the names of the columns that are returned by your query so they are more readable and understandable. Consider this query that returns the salaries and commissions for each employee:
1 select sal,comm 2 from emp
What’s SAL? Is it short for sale? Is it someone’s name? What’s COMM? Is it communication? You want the results to have more meaningful labels.
To change the names of your query results, use the AS keyword in the form original_name AS new_name. Some databases do not require AS, but all accept it:
1 select sal as salary, comm as commission 2 from emp SALARY COMMISSION ------- ---------- 800 1600 300 1250 500 2975 1250 1400 2850 2450 3000 5000 1500 0 1100 950 3000 1300
AS keyword to give new names to columns returned by your query is known as aliasing those columns. The new names that you give are known as aliases. Creating good aliases can go a long way toward making a query and its results understandable to others.