Question

I have a three mysql database table which contains the call record of the customer company. I want to fetch the data from the database for a company group by per hour. If there is no data for an hour, it should return Zero.

I am executing this query, but am getting the result for that hour only for which there is a data in the database.

This is my query.

select ph_Plans.Comp_ID, Plan_Type, ph_Companies.CompanyName,
    (sum(call_length_billable)*100)/(Plan_Limit*60) as total,
    hour(calldate)
from ph_Plans
join ph_Companies
    on ph_Companies.Comp_ID = ph_Plans.Comp_ID
join cdr
    on cdr.CompanyName = ph_Companies.CompanyName
where Plan_Type='Per_Min'
    and date(calldate)='2012-10-01'
    and ph_Companies.CompanyName='"ReadySpace-EN"'
group by hour(calldate);

This is the result that am getting.

+---------+-----------+-----------------+--------+----------------+
| Comp_ID | Plan_Type | CompanyName     | total  | hour(calldate) |
+---------+-----------+-----------------+--------+----------------+
|      44 | Per_Min   | "ReadySpace-EN" | 3.7467 |              1 |
|      44 | Per_Min   | "ReadySpace-EN" | 9.4933 |             18 |
|      44 | Per_Min   | "ReadySpace-EN" | 1.6600 |             20 |
|      44 | Per_Min   | "ReadySpace-EN" | 3.7333 |             21 |
|      44 | Per_Min   | "ReadySpace-EN" | 4.6067 |              2 |
|      44 | Per_Min   | "ReadySpace-EN" | 7.6533 |             23 |
+---------+-----------+-----------------+--------+----------------+

But I want the result from zeroth hour to 23 hour. If no data then it should return zero.

Answer 1

When doing a JOIN, you only JOIN on tables that both have data that corresponds to the Columns being JOINed. What you want to do is a LEFT JOIN when you still want results where there is no corresponding data in the other table.

Something like this:

select ph_Plans.Comp_ID, Plan_Type, ph_Companies.CompanyName,
    if(call_length_billable IS NULL, 0, (sum(call_length_billable)*100)/(Plan_Limit*60)) as total,
    ifnull(hour(calldate), 0) hour
from ph_Plans
left join ph_Companies
    on ph_Companies.Comp_ID = ph_Plans.Comp_ID
left join cdr
    on cdr.CompanyName = ph_Companies.CompanyName
where Plan_Type='Per_Min'
    and (date(calldate)='2012-10-01' OR calldate IS NULL)
    and (ph_Companies.CompanyName='"ReadySpace-EN"' OR ph_Companies.CompanyName IS NULL)
group by hour(calldate);