Question

I have two database tables containing similar data – one is the amount of work completed by a process, the other is the amount of errors made by that process.

I would like to display the percentage of right first time work.

My query for counting the number of items by process is:

SELECT Counter.Process, count( Counter.Process ) AS count
                            FROM Counter WHERE (TIME BETWEEN '2012-07-01 00:00:00' AND '2012-07-06 23:59:59')
                            GROUP BY Counter.Process
                            ORDER BY count DESC

The above gives me a list similar to:

Process    | count
-------------------
Process A  | 40
Process B  | 32
Process C  | 102
Process D  | 23

I have a second table with the same fields in it for recording errors, called ‘Errors’.

By using the same query (but changing the table names obviously) I can get a list of processes and errors.

What I want to do is create a PHP web page showing the percentage of errors per process.

My problem is if I create the two queries separately, when I loop through them using a PHP Where loop I don’t know how to make the calculation to show the percentage.

I tried using a UNION between the two SQL queries, but I can’t get it to show the two different count readings against the process.

Ideally, I’d like a way to show the data like this:

Process   | Counter.count | Errors.count
Process A     40              2
Process B     32              0
Process C     102             18
Process D     23              8

I would really appreciate any advice/suggestions as to how I can accomplish this – if you need more info on my database tables, please let me know

Thanks for reading

S

Answer 1

You could use a sub-query:

SELECT Counter.Process, count( Counter.Process ) AS Count,
      (SELECT count(Errors.Process) 
         FROM Errors
        WHERE Process=Counter.Process 
          AND (TIME BETWEEN '2012-07-01 00:00:00' AND '2012-07-06 23:59:59')) AS Errors
                            FROM Counter WHERE (TIME BETWEEN '2012-07-01 00:00:00' AND '2012-07-06 23:59:59')
                            GROUP BY Counter.Process
                            ORDER BY count DESC

Regards,
Neil.