不同表格中具有分组功能的两个字段的计数不起作用

Question

I have three table a, b and c in mysql. a has events, b has ticket categories for each event of a, and c has tickets each of b. So a pure relational datbase. What i'm trying to find out is the count of total ticket categories and total tickets each of the event a has.

I had tried like this:

SELECT a. * , COUNT( b.at_id ) AS totTktCat, COUNT( c.bt_id ) AS totTkts
FROM a_table a
JOIN b_table b
USING ( at_id ) 
JOIN c_table c
USING ( bt_id ) 
GROUP BY a.at_id

but no luck, the totals are wrong.

A little help from the mysql gurus will help.

I have added an sql fiddle: http://sqlfiddle.com/#!9/ec8b0/1 .

I'm getting total like this

at_id   at_cat  at_event    totTktCat   totTkts
1       1       aevent1     6           6
2       2       aevent2     2           2

which is wrong.

MY expected output is

\nat_id at_cat at_event COUNT(bt_ticktgrp) COUNT(ct_tickets) \n2 2 aevent2 2 4 \n

For the sql fiddle: http://sqlfiddle.com/#!9/ebc9ea6

Answer 1

As per your given description, i have written query like this..

SELECT a.at_id,a.at_cat,a.at_event,count(*) as bt_ticktgrp,(SELECT count(*) FROM `b_table` b JOIN `c_table` c ON c.bt_id=b.bt_id where b.at_id=a.at_id) as ct_tickets  FROM `a_table` a JOIN `b_table` b
ON a.at_id=b.at_id
GROUP BY a.at_cat;

Here i have grouped outer one with table a and inner one with table c by mapping it with table b .

ie With each id of table a it joins table b and table c .

Hope this solves your query.