左外连接

LEFT OUTER JOIN 左外连接

• [ ] 需求：查询所有分类，如果该分类下没有商品，则不显示该分类
• [ ] 实现：

  
  SELECT 
    `goods`.`id`, 
    `goods`.`title`, 
    `goods`.`price`, 
    `goods`.`cate_id`, 
    `cate`.`id`, 
    `cate`, 
    `cate.title` 
        FROM 
            `goods` 
        LEFT OUTER JOIN 
            `category` AS `cate` 
        ON 
            `goods`.`cate_id` = `cate`.`id`;

const cate = await this.ctx.model.Category.findAll({ include: [{ model: this.ctx.model.Goods, as: 'goods', attributes:['title', 'price'], // 实现 左外连接 required: true, }], distinct: true });