Question

I have a product order table in mysql. It’s like this:

create table `order`
  (productcode int,
   quantity tinyint,
   order_date timestamp,
   blablabla)

then, to get rate of rise, i wrote this query:

SELECT thismonth.productcode,
       (thismonth.ordercount-lastmonth.ordercount)/lastmonth.ordercount as riserate
  FROM ( (SELECT productcode,
                 sum(quantity) as ordercount
            FROM `order`
            where date_format(order_date,'%m') = 12
            group by productcode) as thismonth,
          (SELECT productcode,
                  sum(quantity) as ordercount
             FROM `order`
             where date_format(order_date,'%m') = 11
             group by productcode) as lastmonth)
WHERE thismonth.productcode = lastmonth.productcode
ORDER BY riserate;

but it runs about 30s on my pc(200000 records, 200MB(include other fields)).
Are there any way to increase query speed? I already create index for productcode field.

I thought the reason of low performance is ‘GROUP BY’, is there any different way?

I tried your answers, but all of them seems not work, and I was wondering if there is something wrong with index(it’s not me who created them), so I delete all index and re-created them, everything goes fine — It only takes 3-4s. And difference between my query and yours is not very obvious. But REALLY thanks you guys, I learned a lot 🙂

Answer 1

Try adding an index on (ORDER_DATE, PRODUCTCODE) and change the query to eliminate the use of the DATE_FORMAT function, as in:

SELECT thismonth.productcode,
       (thismonth.ordercount-lastmonth.ordercount)/lastmonth.ordercount as riserate   
  FROM ( (SELECT productcode,
                 sum(quantity) as ordercount
            FROM `order`
            WHERE ORDER_DATE BETWEEN '01-12-2010' AND '31-12-2010'
                  GROUP BY PRODUCTCODE) as thismonth,
         (SELECT productcode,
                 sum(quantity) as ordercount
            FROM `order`
            WHERE ORDER_DATE BETWEEN '01-11-2010' AND '30-11-2010'
            group by productcode) as lastmonth)
  WHERE thismonth.productcode = lastmonth.productcode
  ORDER BY riserate;

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