Mybatis one-to-many pass multiple parameters and custom parameters

question:

Assuming that a method with a query parameter x is passed in, and this parameter is also required in the subquery,
how to bring this parameter into the subquery b

General one-to-many query method:

    /**
     * 按User表中platform查询User
     */
    @Select("select * from user where pid = #{id}")
    List<User> findUsers(int id);

    /**
     * 一对多查询
     */
    @Select("select * from platform where 1 = 1")
    @Results({
            /*@Result(property = "id" , column = "id"),*/
            @Result(property = "users",
                    /*javaType = List.class,*/
                    //对platform表中id属性进行一对多查询
                    column = "id",
                    many = @Many(select = "mybatis.mapper.HelloMapper.findUsers")
            )
    })
    List<Platform> getPlatforms();

• findUsers needs to pass in a parameter -> that is, the id in the platform table can be automatically brought in for one-to-many query
• @Result中column = "id"
• Indicates passing each value of the id column in the parent query to the subquery for one-to-many query

solution

• Table shoppingcart: The shopping cart mainly includes the merchant id field, product id and information, customer id, etc.
• In order for a customer to display the merchant in the shopping cart first, and then display the merchandise in the merchant, a customer id needs to be passed in
• Querying merchants requires customer id as the query condition, and querying products requires two conditions: merchant id and customer id
• If the above method is used, (there is no customer id in the merchant table), the customer parameter cannot be passed
• (Assuming that only one merchant id parameter is passed, both parameters of the subquery will be set to the merchant id value for query)

Idea: Put the customer id into the query and save it, and give him an alias

• After this, the customer id can be passed to the subquery

/**
     * 按顾客id查询其购物车（商家->商品 一对多查询）
     * @param consumerId 顾客id
     * @return 购物车商品列表
     */
    @Select("select distinct saler.id,saler.shopname,#{consumerId} as consumerId from shoppingcart \n" +
            "join saler on saler.id = shoppingcart.salerId \n" +
            "where consumerId = #{consumerId}")
    @Results(
            @Result(
                    property = "goods",
                    column = "{salerId = id,consumerId = consumerId}",
                    many = @Many(select = "cn.datacharm.springbootvuecli.dao.CartMapper.findGoodsBySalerId")
            )
    )
    List<Shop> findCartById(Integer consumerId);

    @Select("select \n" +
            "sid,consumerId,productName,price,photo,\n" +
            "shoppingcart.salerId,\n" +
            "shoppingcart.productId,\n" +
            "shoppingcart.amount\n" +
            "from shoppingcart\n" +
            "join saler_inventory on shoppingcart.salerId = saler_inventory.salerId\n" +
            "and shoppingcart.productId = saler_inventory.productId\n" +
            "where shoppingcart.salerId = #{salerId}\n"+
            "and consumerId = #{consumerId}" )
    List<Goods> findGoodsBySalerId(Integer salerId,Integer consumerId);

• @Result中column = "{salerId = id,consumerId = consumerId}"
• Indicates that the id column and consumerId column are taken out
• The id column value uses saleserId, and the consumerId column uses consumerId to represent (similar to aliases, corresponding to subquery parameters)
• Then make a subquery with these two parameters