将单个表中的两个不同值相加并减去其值并按pcode对它们进行分组

Question

i have 1 table named rsales. and let say for example i have this following values from my table "rsales"

id | total | discount |  profit | remarks | p_code |
 1 |  20   |   2      |    5    |  sales  |  1234  |
 2 |  20   |   4      |   10    |  sales  |  1234  |
 3 |  20   |   6      |   15    |  sales  |  1234  | 
 5 |  20   |   2      |    5    |  return |  1234  |
 6 |  20   |   4      |   10    |  return |  1234  |
 7 |  10   |   5      |    5    |  sales  |  3333  |
 8 |  10   |   5      |    5    |  sales  |  3333  |
 9 |  10   |   5      |    5    |  sales  |  3333  |
10 |  10   |   5      |    5    |  return |  3333  |
11 |  10   |   5      |    5    |  return |  3333  |

my problem is that i want to sum all values where remarks = "sales" and sum all values where remarks = "return" and then after getting its sum i want to subtract total sum where remarks = 'sales' to total sum where remarks = 'return' and group them by pcode. so the following output must be something like this.

 | total | discount |  profit |  p_code |
 |  20   |   6      |   15    |   1234  |
 |  10   |   5      |   5     |   3333  |

i have this ff code but it can only sum values where remarks = 'return'

$result1 = mysql_query ("SELECT sum(total)  as tot,sum(discount) as dis, sum(profit) as prof   FROM rsales WHERE remarks ='return' GROUP by p_code ");

Answer 1

You need conditional summation. Assuming that remarks only takes on the values of "sales" and "returns", then the following is a relatively simple way to do this:

SELECT sum(case when remarks = 'sales' then total else - total end) as tot,
       sum(case when remarks = 'sales' then discount else - discount end) as discount,
       sum(case when remarks = 'sales' then profit else - profit end) as profit,
       p_code 
FROM rsales
GROUP by p_code;