使用 Sequelize 计算相关模型和限制

Question

我有一个有效的 Sequelize 查询，它以这种方式获取模型，包括相关模型的数量：

    const elements = await ElementsModel.findAll({
      attributes: {
        include: [[Sequelize.fn("COUNT", Sequelize.col("related.id")), "related_total"]]
      },
      include: [
        {
          model: RelatedModel,
          attributes: [],
        }
      ],
      group: ['elements.id']
    });

查询效果很好，但现在我需要包含一个 offset 和 limit 子句用于分页，例如：

    const elements = await ElementsModel.findAll({
      limit: 10,
      offset: 0,
      attributes: {
        include: [[Sequelize.fn("COUNT", Sequelize.col("related.id")), "related_total"]]
      },
      include: [
        {
          model: RelatedModel,
          attributes: [],
        }
      ],
      group: ['elements.id']
    });

由于包含字段和limit 子句的组合，查询中断并且不再工作，生成无效查询，例如：

SELECT `elements`.* 
FROM (
  SELECT `elements`.`id`, `elements`.`type`, COUNT(`related`.`coupon_id`) AS `related_total` 
  FROM `elements` AS `elements` GROUP BY `elements`.`id` LIMIT 0, 20
) AS `elements` 
LEFT OUTER JOIN `related` AS `related` ON `elements`.`id` = `related`.`elements_id`;

Sequelize 有什么方法可以解决这个问题？

Answer 1

要正确使用limit 和offset 选项，您需要使用带有Sequelize.literal 而不是Sequelize.fn 的子查询，并完全删除include 和group 选项。

const elements = await ElementsModel.findAll({
      limit: 10,
      offset: 0,
      attributes: {
        include: [
  // correct a table name and fields if needed
  [Sequelize.literal("(SELECT COUNT(*) FROM Related where Related.elementId=Elements.id)"), "related_total"]
      ]
      },
    });