MYSQL计数为，Group By，JSON等效

Question

是否有

的等价物

mysql_query("SELECT subcategory, COUNT(*) AS subcate FROM database GROUP BY subcategory");

在Js-Json中，我可以计算出有多少独特的子类别，并将它们打印在JSON数组中而不在mysql_query过滤它们？

假设我使用

从数据库获取完整表

mysql_query("SELECT * FROM database");

然后我将它放入json_encode($array);然后我可以计算独特的子类别并从该JSON数组中打印出来吗？

JSON DATA

[{"category":"fish","subcategory":"angel","name":"angelfish juvenille"},{"category":"fish","subcategory":"angel","name":"angelfish adult"},{"category":"fish","subcategory":"clownfish","name":"clownfish juvenille"},{"category":"fish","subcategory":"clownfish","name":"clownfish adult"]

Answer 1

您需要对数据列表进行简单的缩减。您为每个子类别保留一个带有键的对象，该值是具有该特定子类别的元素数量：

＆＃13;

＆＃13;

 var data = [{"category":"fish","subcategory":"angel","name":"angelfish juvenille"},{"category":"fish","subcategory":"angel","name":"angelfish adult"},{"category":"fish","subcategory":"clownfish","name":"clownfish juvenille"},{"category":"fish","subcategory":"clownfish","name":"clownfish adult"}]

var result=  data.reduce((all, element) => { 
   all[element.subcategory] = (all[element.subcategory] || 0) +1;
   return all
}, {});

console.log(result);

＆＃13;

＆＃13;

＆＃13;