DISTINCT keyword allows you to find unique values in a column.
Once a table starts getting a lot of data in it, some columns will contain duplicate values.
For example, many Individuals share first names and surnames. Most of the time this isn't a problem. But sometimes you will want to find out how many unique values there are in a column. To do this you can use the
SELECT DISTINCT(FirstName) FROM Individual;
In this example, using the
DISTINCT keyword, all customers with the same first name are treated as one. This results in only one entry for Homer (even though there are three different entries in total).