[TOC] ### 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 }); ~~~