如何用group by计算mysql数据

Question

I have a php web page and I got a problem with counting data using group by in mysql query

When any question submitted, id is automatically add and idqu=0 if question replied then idqu is equal to replied question's id

My table and data

id idqu question answer    user    date

1   0   quest1             test    28042014

2   0   quest2             scott   29042014

3   2   reply1             andy    01052014

4   0   quest3             test    01052014

5   4   reply2             scot    01052014

My question is how can I count question's reply?

quest1 (0)

quest2 (1)

quest3 (1)

Answer 1

This query does the job. I gave the table the name "tbl"

Select q.id, count(a.id) as answers

From tbl q

Left join tbl a on a.idqu=q.id

Where q.idqu=0

Group by q.id