Removing duplicates

- [Instructor] There will be times when you may want to know…all the different values of a column in your result,…without duplication.…For this purpose SQL provides the SELECT DISTINCT statement,…for example if we use the world database,…and I SELECT Continent from Country.…You notice I get 239 rows and many of them are duplicates,…this isn't telling me how different continents there are.…

So for this we have SELECT DISTINCT,…if I say SELECT DISTINCT Continent from Country,…now we only get seven rows,…that's because there's really just a few continents…according to the divisions…using this database there are seven,…and so using the SELECT DISTINCT statement,…you get only unique results.…For another example, let's go to the Exercise File here,…and we'll just copy all of this, and paste it in,…and for this we're gonna use the test database,…and what we have here is a simple table, called test…with two columns, a and b, and they're both integers,…and I add a bunch of rows to this and run select,…and you see we have now this table with 10 rows,…