Counting number of grouped rows in mysql

Question

In a table xyz I have a row called components and a labref row which has labref number as shown here

Table xyz

labref             component
NDQA201303001         


        

Answer 1

I found the solution. So, if you want to count quantity of groups, not quantity of elements in each group, and return duplicate value to every group record in result table, you should use OVER() clause on you'r count function.

So, for example above the solution would be

SELECT component, COUNT(*) OVER() as number_of_components FROM `xyz` 
WHERE labref = 'NDQA201303001' 
GROUP BY component

I suppose that works with any query that use GROUP BY, additional info, check in the link above.