mysql - 如何计算类别中的产品

Question

我有一个嵌套集合模型中的类别表，我想用他们有多少产品来分类。像这样的东西

Categories-(6)
    Cars-(4)
      BMW-(2)
      Opel-(1)
      Mercedes-(1)
    Trucks-(2)
      Man-(1)
      Mercedes-(1)

我有两张桌子，categories并且types

分类：id,name,level,lft,rgt

类型：id,category_id,name

现在我可以只列出这些类别：

$categories = Doctrine_Core::getTable('Category')
  ->createQuery('c1')
  ->select('c1.id, c1.level, c1.name')
  ->innerJoin('c1.Category c2 ON ( c1.lft BETWEEN c2.lft AND c2.rgt )')
  ->andWhere(' c2.id = ?', $id)
  ->andWhere('c1.level > 0')
  ->andWhere('c1.level < c2.level+3')
  ->groupBy('c1.id')
  ->orderBy('c1.lft')
  ->execute();

反正有没有像上面那样返回计数？

Answer 1

select table1.name,table2.countcars
from categories as table1 right join 
     (select category_id,count(*) as countcars 
        from cars group by category_id) as table2 
  on table1.id=table2.category_id;

你会得到

    BMW-(2)
    Opel-(1)
    Mercedes-(1)

从上面的查询

对于 Cars-(4) 你只需要这样做

select count(*) as numberOfCars from cars;