Mysql select multiple count giving wrong values

Question

I'm trying to find a patient's appointments and messages count. My table records are like below 3 table patient, appointments and messages
Patient table

pid     fname   lname
1      john     sid
2      rother   ford
3      megan    rough
4      louis    kane

appointments table

id  pid     appointment_date
1   1   2015-08-04
2   2   2015-08-05
3   1   2015-08-06
4   1   2015-08-07
5   3   2015-08-07
6   2   2015-08-08
7   4   2015-08-13
8   1   2015-08-12

Messages table

id  pid     description     message_date
1   2        join           2015-08-04
2   2        update         2015-08-05
3   3        join           2015-08-05
4   4        update         2015-08-10
5   3        test           2015-08-07

So if write query to find counts i'm getting wrong values

SELECT pd.fname,pd.lname , pd.pid, COUNT( a.id ) AS app_cnt, COUNT(   m.id   ) AS mes_cnt
FROM patient pd
LEFT OUTER JOIN appointments a   ON a.pid = pd.pid
LEFT OUTER JOIN messages m ON m.pid = pd.pid
GROUP BY pd.pid
ORDER BY pd.pid  

fname   lname   pid     app_cnt     mes_cnt
john    sid     1         4            0
rother  ford    2         4            4
megan   rough   3         2            2
louis   kane    4         1            1

Here pid 1 have 4 appointments and 0 messages, pid 2 have 2 appointments and 2 messages but getting wrong values.

Can someone please help to resolve this issue. I'm not interested in writing sub queries for this.

Functionality looks simple but I'm really facing problem for writing query.

Anymore suggestions please.

Answer 1

After thoroughly analysing your problem and tables, It cannot be done directly using simple query as LEFT OUTER JOIN is returning some superfluous records, that's why to filter it, you will have to use temporary table and modify the query as:

Select temp.fname, temp.lname, temp.pid, a_count, count(m.pid) as m_count from
(SELECT fname,lname,pd.pid, count(a.pid) as a_count
FROM patients pd
LEFT OUTER JOIN appointments a   ON a.pid = pd.pid group by pd.pid) temp
LEFT OUTER JOIN messages m ON m.pid = temp.pid
group by temp.pid

Explanation:

It will join patients and appointments table and group them by pid so that messages from message table do not repeat for each patients.pid .

The wrong result is as a result of left outer join as it is giving wrong results for this query

SELECT *
FROM patients pd
LEFT OUTER JOIN appointments a   ON a.pid = pd.pid
LEFT OUTER JOIN messages m ON m.pid = pd.pid

Since we need to limit the results of first two joins, hence temporary table is necessary.