我需要计算每个类别的计数（vendors.id）。ie:每个类别（不是子类别）有多少供应商
我使用cakephp3.6框架和mysql作为数据库
我尝试了所有可能的方法，我知道，但没有找到任何解决办法。有人能帮我吗，这对我的项目很重要
[更新]我使用的sql查询：

SELECT cat.id,cat.name ,COUNT(`vendor_id`) AS vendor_count FROM `vendor_services` JOIN `categories` ON(`vendor_services`.`category_id` = `categories`.`id`) JOIN `categories` AS cat ON(categories.category_id = cat.id) WHERE 1 GROUP BY cat.id

[更新]下面是创建相应表的sql

-- phpMyAdmin SQL Dump
-- version 4.7.0
-- https://www.phpmyadmin.net/
--
-- Host: 127.0.0.1
-- Generation Time: Dec 04, 2018 at 10:50 AM
-- Server version: 10.1.24-MariaDB
-- PHP Version: 7.1.6
SET SQL_MODE = "NO_AUTO_VALUE_ON_ZERO";
SET AUTOCOMMIT = 0;
START TRANSACTION;
SET time_zone = "+00:00";
--
-- Database: `demo123`
--
-- --------------------------------------------------------
--
-- Table structure for table `categories`
--
CREATE TABLE `categories` (
  `id` int(11) NOT NULL,
  `category_id` tinyint(4) NOT NULL,
  `name` varchar(60) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
--
-- Dumping data for table `categories`
--
INSERT INTO `categories` (`id`, `category_id`, `name`) VALUES
(1, 0, 'Books'),
(2, 0, 'Electronics'),
(3, 0, 'Garden'),
(4, 1, 'Novel'),
(5, 1, 'Science'),
(6, 1, 'Story'),
(7, 2, 'Mobile'),
(8, 2, 'Tablet'),
(9, 2, 'Headphone'),
(10, 3, 'Pumps'),
(11, 3, 'Pipes');
-- --------------------------------------------------------
--
-- Table structure for table `vendors`
--
CREATE TABLE `vendors` (
  `id` int(11) NOT NULL,
  `name` varchar(60) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
--
-- Dumping data for table `vendors`
--
INSERT INTO `vendors` (`id`, `name`) VALUES
(1, 'VR Enterprizes'),
(2, 'RR Vendors'),
(3, 'JK Suppliers');
-- --------------------------------------------------------
--
-- Table structure for table `vendor_services`
--
CREATE TABLE `vendor_services` (
  `id` int(11) NOT NULL,
  `vendor_id` int(11) NOT NULL,
  `category_id` int(11) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
--
-- Dumping data for table `vendor_services`
--
INSERT INTO `vendor_services` (`id`, `vendor_id`, `category_id`) VALUES
(1, 1, 4),
(2, 1, 5),
(3, 1, 6),
(4, 1, 11),
(5, 2, 7),
(6, 2, 8),
(7, 2, 9),
(8, 3, 10),
(9, 3, 11);
--
-- Indexes for dumped tables
--
--
-- Indexes for table `categories`
--
ALTER TABLE `categories`
  ADD PRIMARY KEY (`id`),
  ADD KEY `category_id` (`category_id`);
--
-- Indexes for table `vendors`
--
ALTER TABLE `vendors`
  ADD PRIMARY KEY (`id`);
--
-- Indexes for table `vendor_services`
--
ALTER TABLE `vendor_services`
  ADD PRIMARY KEY (`id`),
  ADD KEY `vendor_id` (`vendor_id`),
  ADD KEY `category_id` (`category_id`);
--
-- AUTO_INCREMENT for dumped tables
--
--
-- AUTO_INCREMENT for table `categories`
--
ALTER TABLE `categories`
  MODIFY `id` int(11) NOT NULL AUTO_INCREMENT, AUTO_INCREMENT=12;
--
-- AUTO_INCREMENT for table `vendors`
--
ALTER TABLE `vendors`
  MODIFY `id` int(11) NOT NULL AUTO_INCREMENT, AUTO_INCREMENT=4;
--
-- AUTO_INCREMENT for table `vendor_services`
--
ALTER TABLE `vendor_services`
  MODIFY `id` int(11) NOT NULL AUTO_INCREMENT, AUTO_INCREMENT=10;COMMIT;

可分类的

$this->hasMany(‘Subcategories’, [ 'className'=> ‘Categories’,
            'foreignKey' => 'category_id',
            'conditions' => ['category_id!= 0']
        ]);
$this->belongsTo('MainCategories', [
                'className'=> ‘Categories’,
                    'foreignKey' => 'category_id',
        ]);