我在PostgreSQL数据库上有两个表，合同和付款。一份合同完成了多次付款。

我有以下两个模型：

 module.exports = function(sequelize, DataTypes) {
  var contracts = sequelize.define('contracts', {
    id: {
      type: DataTypes.INTEGER,
      autoIncrement: true
    }
  }, {
    createdAt: false,
    updatedAt: false,
    classMethods: {
      associate: function(models) {
        contracts.hasMany(models.payments, {
          foreignKey: 'contract_id'
        });
      }
    }
  });


  return contracts;
};

module.exports = function(sequelize, DataTypes) {
  var payments = sequelize.define('payments', {
    id: {
      type: DataTypes.INTEGER,
      autoIncrement: true
    },
    contract_id: {
      type: DataTypes.INTEGER,
    },
    payment_amount: DataTypes.INTEGER,
  }, {
    classMethods: {
      associate: function(models) {
        payments.belongsTo(models.contracts, {
          foreignKey: 'contract_id'
        });
      }
    }
  });


  return payments;
};

我想对每个合同的所有付款进行汇总，并使用以下功能：

models.contracts.findAll({
    attributes: [
        'id'
    ],
    include: [
    {
        model: models.payments,
        attributes: [[models.sequelize.fn('sum', models.sequelize.col('payments.payment_amount')), 'total_cost']]
    }
    ],
    group: ['contracts.id']
})

但它生成以下查询：

SELECT "contracts"."id", "payments"."id" AS "payments.id", sum("payments"."payment_amount") AS "payments.total_cost" 
FROM "contracts" AS "contracts" 
LEFT OUTER JOIN "payments" AS "payments" ON "contracts"."id" = "payments"."contract_id" GROUP BY "contracts"."id";

我不要求选择payments.id，因为我必须将其包括在我的汇总或按功能分组中，如错误消息中所述：

可能未处理的SequelizeDatabaseError：错误：列“ payments.id”必须出现在GROUP BY子句中或在聚合函数中使用

我在这里想念什么吗？我正在关注这个答案，但是即使到那里我也不明白SQL请求如何有效。