Count of groups

Question

Is there a way to get a count of groups in mysql?

For example I have 4 rows

cat1 cat2 cat1 cat3

I would like a count of categories, i.e 3

Is this possible?

Thanks

Answer 1

select count(distinct(cat)) from table;

Answer 2

Not sure if this is the "purest" answer, but you could do this with a nested select query

select count() from ( select catagory, count() from table_name group by catagory) A