คือผมต้องการจะ Sum ข้อมูลของสินค้าประเภทเดียวกันครับ ว่าในหนึ่งวันให้แสดงยอดที่ขายได้ จนครบหนึ่งเดื่อนครับ

Select date_sale,
Sum(if(prod_id='aa',amount,0)) as aa,
Sum(if(prod_id='bb',amount,0)) as bb
From tablename
Where date_sale between startdate and lastdate
Group by date_sale

<?php
function x($prod_ar, $st, $en){
	$sum = '';
	foreach($prod_ar as $id){
		$sum .= ", sum(if(prod_id='$id',amount,0)) as `$id` ";
	}
	return "Select date_sale" . $sum . " From tablename Where date_sale between '$st' and '$en' Group by date_sale";
}
function show_table($rs){
	while($ro = $rs->fetch_assoc()){
		.....
		.....
	}
}
//////////////////////////////////////////////////////
$db = new mysqli('host','user','password', 'database');
if ($db->connect_errno) {
	echo 'Connection failer<BR><a href="' . $PHP_SELF . '?' . $_SERVER ['QUERY_STRING'] . '">Refresh</a>';
	exit ();
}
$db->query('SET NAMES utf8');
//////////////////////////////////////////////////////
$show_count_column = 5;
$group_product = array('RB', 'MN', 'FG');
foreach($group_product as $gp){
	$prod_rs = $db->query("select prod_id from table_product_list where left(prod_id,2)= '$gp' order by prod_id");
	$prod_ar = array();
	while($ro = $prod_rs->fetch_assoc()){
		$prod_ar[]=$ro['prod_id'];
		if(count($prod_ar)==$show_count_column){
			$sql=x($prod_ar, '2017-01-01', '2017-01-31');
			$p_rs = $db->query($sql);
			/////////////////////////
			show_table($p_rs);
			/////////////////////////
			$prod_ar=array();
		}
	}
	if(count($prod_ar)>0){
		$sql=x($prod_ar, '2017-01-01', '2017-01-31');
		$p_rs = $db->query($sql);
		/////////////////////////
		show_table($p_rs);
		/////////////////////////
	}
}

Select s.date_sale,
Sum(if(left(s.prod_id,2)='aa', b.amount,0)) as aa_in,
Sum(if(left(s.prod_id,2)='aa', s.amount,0)) as aa_out,
Sum(if(left(s.prod_id,2)='bb', b.amount,0)) as bb_in,
Sum(if(left(s.prod_id,2)='bb', s.amount,0)) as bb_out,
Sum(if(left(s.prod_id,2)='cc', b.amount,0)) as cc_in,
Sum(if(left(s.prod_id,2)='cc', s.amount,0)) as cc_out

From table_prod p
Left join sale s on p.prod_id=s.prod_id and s.date_sale between startdate and lastdate
Left join buy b on p.prod_id=b.prod_id and b.date_buy between startdate and lastdate
Group by date_sale