Combining database queries

Question

How can these SQL-queries to extract statistics from my database be combined for better performance?

$total= mysql_query("SELECT COUNT(*) as number, SUM(order_total) as sum FROM history");
$month = mysql_query("SELECT COUNT(*) as number, SUM(order_total) as sum FROM history WHERE date >= UNIX_TIMESTAMP(DATE_ADD(CURDATE(),INTERVAL -30 DAY))");
$day = mysql_query("SELECT COUNT(*) as number, SUM(order_total) as sum FROM history WHERE date >= UNIX_TIMESTAMP(CURDATE())");

Answer 1

If you want to all the data in a single query, you have two choices:

1. Use a UNION query (as sugested by bishop in his answer)
2. Tweak a query to get what you need in a single row

I'll show option 2 (option 1 has been already covered).

Note: I'm using user variables (that stuff in the init subquery) to avoid writing the expressions again and again. Also, to filter the aggregate data, I'm using case ... end expressions.

select 
    -- Your first query:
    count(*) as number, sum(order_total) as `sum`
    -- Your second query:
  , sum(case when `date` <= @prev_date then 1 else 0 end) as number_prev
  , sum(case when `date` <= @prev_date then order_total else 0 end) as sum_prev
    -- Your third query:
  , sum(case when `date` <= @cur_date then 1 else 0 end) as number_cur
  , sum(case when `date` <= @cur_date then order_total else 0 end) as sum_cur
from (
         select @cur_date := unix_timestamp(curdate())
              , @prev_date := unix_timestamp(date_add(curdate(), interval -30 day))
     ) as init
   , history;

Hope this helps