Question

我从两张卡车和订单计算每月的平均汽油数量。到目前为止，我每个月都获得平均值，我可以通过按日期排序和外部SQL的平均值来获得。

我希望得到相同的值，但现在它应该返回订单的所有细节。我将使用它来使用行映射器映射到java以获得一对多关系，并使用具有订单列表的dto类。

select truckId, truckcode, purchasedDate, descriptions, avg(avgPetrolQty) as avgPerMonth from ( 
SELECT  t.truckId, t.truckCode, t.purchasedDate, t.descriptions, 
COALESCE(monthname(orderDate),'Not Announced') as month, 
IFNULL (avg(petrolQty),0) as avgPetrolQty 
from truck t left join orderz o 
on t.truckId = o.truckId 
where t.truckId = :t.truckId 
group by t.truckCode, orderDate, 
year(orderDate) 
) group by truckcode

到目前为止，这给了我每辆卡车的预期平均每月单一价值，但我想将剩余的订单细节添加到它，例如应该通过id获得的完全加入。我试过这个，但显然不准确

 select t.truckId, t.truckCode, t.purchasedDate, 
t.descriptions, o.orderId, o.petrolQty, o.orderDate, avg(avgPetrolQty) as avgPerMonth, o.truckId from (truck t 
SELECT  t.truckId, t.truckCode, t.purchasedDate, t.descriptions, o.orderId, o.petrolQty, o.orderDate,  o.truckId 
COALESCE(monthname(o.orderDate),'Not Announced') as month,
IFNULL (avg(o.petrolQty),0) as avgPetrolQty  
left join orderz o 
on t.truckId = o.truckId 
where t.truckId = :t.truckId 
group by t.truckId, o.orderDate 
) 
from truck t left join orderz o 
on t.truckId = o.truckId 
where T.truckId = :t.truckId 
group by t.truckId, o.orderDate

每月平均值是最重要的信息。现在我只想获得卡车的全部细节（这意味着所有属于卡车的订单）

SQL表

DROP TABLE IF EXISTS truck;
CREATE TABLE truck (
  truckId INT NOT NULL AUTO_INCREMENT,
  truckCode VARCHAR(255) NOT NULL UNIQUE,
  purchasedDate timestamp  NOT NULL,
  descriptions VARCHAR(255) NOT NULL,
  PRIMARY KEY (truckId)
);

DROP TABLE IF EXISTS orderz;
CREATE TABLE orderz (
  orderId INT NOT NULL AUTO_INCREMENT,
  petrolQty DOUBLE NOT NULL,
  orderDate timestamp NOT NULL,
  truckId INT,
  PRIMARY KEY (orderId),
  FOREIGN KEY (truckId) REFERENCES truck(truckId)
  ON UPDATE CASCADE
  ON DELETE CASCADE
);

Answer 1

要做到这一点，你的外部查询应该或多或少地作为一个复印机，所以你在内部查询中完成所有工作并复制到外部select语句只有外部select语句才能做到的事情是获得平均值的平均值

select truckId,  truckCode,  purchasedDate, 
descriptions, orderId, petrolQty, orderDate, avg(avgPetrolQty) as avgPerMonth, truckId from (
SELECT  t.truckId, t.truckCode, t.purchasedDate, t.descriptions, o.orderId, o.petrolQty, o.orderDate,
COALESCE(monthname(o.orderDate),'Not Announced') as month,
IFNULL (avg(o.petrolQty),0) as avgPetrolQty  
from truck t left join orderz o 
on t.truckId = o.truckId 
where t.truckId = :t.truckId 
group by  t.truckCode, o.orderId, o.orderDate
) group by truckCode, orderId

这就是我在java中使用RowMapper和namedParameterJdbcTemplate将其映射到id的方式

 public TruckFullDetailDto getTruckFullDetailById (final Integer id) {
     SqlParameterSource namedParameterSource =
                new MapSqlParameterSource("t.truckId", id);
       TruckDetailMapper mapper = new TruckDetailMapper();
       namedParameterJdbcTemplate.query(fullTruckDetailsql, namedParameterSource, mapper);

       TruckFullDetailDto truck = mapper.getDetail();
       return truck;
     }

    /**
     * This is mapper maps one to many relationship.
     */
    public class TruckDetailMapper implements RowMapper<TruckFullDetailDto> {

    private TruckFullDetailDto detail;

     public TruckFullDetailDto mapRow(ResultSet rs, int rowNum)
            throws SQLException {

        if (detail == null) {

            this.detail = new TruckFullDetailDto();

            detail.setTruckId(rs.getInt("truckId"));
            detail.setTruckCode(rs.getString("truckCode"));
            detail.setAvgPerMonth(rs.getDouble("avgPerMonth"));
            detail.setDescriptions(rs.getString("descriptions"));
            detail.setPurchasedDate(rs.getDate("purchasedDate"));
        }

         Order order = new Order ();
         order.setOrderId(rs.getInt("orderId"));
         order.setPetrolQty(rs.getDouble("petrolQty"));
         order.setOrderDate(rs.getDate("orderDate"));
         order.setTruckId(rs.getInt("truckId"));

        this.detail.getOrderList().add(order);
        return null;

    }

     private TruckFullDetailDto getDetail() {
        return detail;
     }

  }

计算sql中的平均值并获得完整的连接语句

1 个答案: