每个shop_id只有一次sql计数

Question

$query = "SELECT shop_id, article_id, design_id FROM shop_tshirts WHERE design_id = '$design'";
$zres = mysql_query($query) or die(mysql_error());
$total = mysql_num_rows($zres);

我使用此代码来获取使用特定$ design的产品数量。

是否可以仅按店铺数量计算产品数量？

此DB结构的示例：

shop_id / article_id / design_id
S01 / A01 / D01
S02 / A02 / D01
S03 / A03 / D01
S03 / A04 / D01

通常使用这种结构，我的代码的结果将是4 ...我想更改代码，因此结果将是3，因为D01在S03中被使用了两次，我想每个商店只计算一次

谢谢！

Answer 1

SELECT distinct shop_id, article_id, design_id FROM shop_tshirts WHERE design_id = '$design'

Answer 2

您必须使用SQL SELECT DISTINCT语句

$query = "SELECT DISTINCT shop_id, article_id, design_id FROM shop_tshirts WHERE design_id = '$design'";

Answer 3

您需要唯一的shop_id值

您不需要article_id或design_id

$query = "SELECT DISTINCT shop_id FROM shop_tshirts WHERE design_id ='$design'";
$zres = mysql_query($query) or die(mysql_error());
$total = mysql_num_rows($zres);