如何使JPQL加入不能使结果翻倍

Question

I have a few entities for quoting items, using JPA/JPQL and Hibernate.

A quote has many quote items, and each item can have 0 or more adjustments. Each adjustment is either a discount or surcharge, and either percentage (ie percentage of the price of the item) or amount (ie a fixed value)

I'm trying to write a JPQL query that will give me the value of all quotes for a given region and user and time period, adding together the price of each quote item for the quote and the value of any adjustments. I nearly have it working but it's not quite right.

String query = "select q.user, q.contact.parent.region, sum( case " +
        " when a.type = :type_surcharge and a.amountType = :amount_type_percentage then ( a.amount * qi.price ) " +
        " when a.type = :type_surcharge and a.amountType = :amount_type_amount then ( a.amount ) " +
        " when a.type = :type_discount and a.amountType = :amount_type_percentage then ( -1 * a.amount * qi.price ) " +
        " else ( -1 * a.amount ) end ) + sum(qi.price) " +
        " from " + Quote.class.getName() + " q " +
        " left join q.quoteItems qi " +
        " left join qi.adjustments a " +
        " where q.date between :from and :to and q.contact.parent.region in :regions group by q.user, q.contact.parent.region";

The problem is that if a quote item has more than one adjustment, then that item appears multiple times in the sum(qi.price) calculation

Can anyone help me with a fix to this query to only include each quote item once in the sum? ( sum( distinct qi.price ) doesn't work) I'm hoping it can be done in a single query if possible.

Edit: It's more wrong than I thought - the query returns null for the summed value if there are quotes present without adjustments, even though I am using left join (?). The only time the data is correct is if: - there is either 0 or 1 adjustments for an item - there is an adjustment for at least one item in all the quotes that pass the region/user/period filters.

Entities (simplified)

@Entity
@DiscriminatorValue(AbstractCollateral.TYPE_QUOTE)
@Table(name="customer_quote", uniqueConstraints={@UniqueConstraint(name="quote_number_uk", columnNames={"number"})})
public class Quote extends AbstractCollateral<QuotedCarePack>
{
  ... other elements

  @OneToMany(fetch = FetchType.EAGER, mappedBy = "parent", cascade = CascadeType.ALL, orphanRemoval=true)
  protected Set<QuotedCarePack> quoteItems;

}

@Entity
@Inheritance(strategy=InheritanceType.JOINED)
@DiscriminatorColumn(name="collateral_type", discriminatorType=DiscriminatorType.STRING, length=10)
@Table(name="abstract_collateral")
public abstract class AbstractCollateral<T extends AbstractCollateralItem<?>> extends AbstractManagedData implements ContactInfo{

  private static final long serialVersionUID = 1L;

  public static final String TYPE_ORDER = "order";
  public static final String TYPE_QUOTE = "quote";

  @Column(name="collateral_type", insertable=true, updatable=false, length=10)
  protected String collateralType;

  @ManyToOne(fetch=FetchType.EAGER)
  @JoinColumn(name="customer_contact_id", nullable=false)
  protected CustomerContact contact;

  @ManyToOne(fetch=FetchType.EAGER)
  @JoinColumn(name="user_id", nullable=false)
  protected User user;
  /**
   * The date the collateral was made (not the sent date, necessarily)
   */
  @Column(name="creation_date", nullable=false)
  @Temporal(TemporalType.TIMESTAMP)
  protected Date date;
}

@Entity(name="quoted_care_pack")
public class QuotedCarePack extends AbstractCollateralItem<Quote> {

  private static final long serialVersionUID = 1L;

  @ManyToOne(fetch=FetchType.EAGER)
  @JoinColumn(name="quote_id", nullable=false)
  protected Quote parent;

  @OneToMany(fetch=FetchType.EAGER, cascade={CascadeType.PERSIST, CascadeType.MERGE})
  @JoinTable
  (
      name="quoted_care_pack_adjustment",
      joinColumns={ @JoinColumn(name="quoted_care_pack_id", referencedColumnName="id") },
      inverseJoinColumns={ @JoinColumn(name="adjustment_id", referencedColumnName="id", unique=true) }
  )
  protected Set<Adjustment> adjustments;
}

@Entity(name="adjustment")
public class Adjustment extends AbstractManagedData {

  private static final long serialVersionUID = 1L;

  @Column(name="amount")
  protected double amount;
  @Column(name="reason", length=100)
  protected String reason;
  @Column(name="type")
  @Enumerated(EnumType.STRING)
  protected AdjustmentType type;
  @Column(name="amount_type")
  @Enumerated(EnumType.STRING)
  protected AdjustmentAmountType amountType;
}

Answer 1

Unfortunately, JPA does not support subqueries in the select clause, which is what you need to do so that the joins to obtain the sum of all adjustments doesn't affect the sum of quoteItems.

This leaves using native SQL, or executing two queries - one for the qi.price sum and another for the adjustments sum:

"select q.user, q.contact.parent.region, sum(qi.price) " +
        " from " + Quote.class.getName() + " q " +
        " left join q.quoteItems qi " +
        " where q.date between :from and :to and q.contact.parent.region in :regions group by q.user, q.contact.parent.region";

and

"select q.user, q.contact.parent.region, sum( case " +
        " when a.type = :type_surcharge and a.amountType = :amount_type_percentage then ( a.amount * qi.price ) " +
        " when a.type = :type_surcharge and a.amountType = :amount_type_amount then ( a.amount ) " +
        " when a.type = :type_discount and a.amountType = :amount_type_percentage then ( -1 * a.amount * qi.price ) " +
        " else ( -1 * a.amount ) end ) " +
        " from " + Quote.class.getName() + " q " +
        " left join q.quoteItems qi " +
        " left join qi.adjustments a " +
        " where q.date between :from and :to and q.contact.parent.region in :regions group by q.user, q.contact.parent.region";