select rows where values equal the result of count(*) group by?

Question

I have a table like this:

Each keyword should have 4 pieces of data.

I want to select the keywords that have less than 4 pieces of data (less than 4 rows).

I used select count(*) from mytable group by keyword to achieve something like this:

how can I select the keywords based on the count(*) result?

Here I want the keyword b from the result grid.

Answer 1

You can either nest your select and use a where clause in the outer select:

select keyword 
from (
    select keyword, count(*) as cnt
    from mytable
    group by keyword
) as t
where cnt < 4

or you can use having which essentially is a shorter form of the above:

select keyword
from mytable
group by keyword
having count(*) < 4