如何使用 createQuery() 在 hibernate 中编写内部连接

Question

我有一个 mysql 内连接查询，它连接数据库中的 3 个表并产生所需的结果集。现在我想使用 session.createQuery() 编写相应的休眠查询。我在我的项目中为这 3 个表创建了模型 class。没有与 3 个表关联的映射。 mysql 查询如下。

select b.ID, b.Date, d.Name, IF(c.Amount < 0, c.Amount * -1, c.Amount) Amount, IF(c.Amount < 0, "Payment", "Receipt") Type from (select TransactionID from TransactionDetail where AccountID = 56) a inner join TransactionHeader b on a.TransactionID = b.ID inner join TransactionDetail c on a.TransactionID = c.TransactionID inner join Account d on c.AccountID = d.ID where c.AccountID <> 56;

现在请告诉我如何使用 hibernate session.createQuery() 编写此查询？请帮助 me.Below 是 3 个表 class 的模型

Accounts.java:

@Entity
@Table(name = "Account")
public class Accounts {
@Id
@GeneratedValue
@Column(name="ID")
private Integer id;

@Column(name="Name")
private String name;

public Accounts() {
    super();
    // TODO Auto-generated constructor stub
}

public Accounts(Integer id, String name) {
    super();
    this.id = id;
    this.name = name;
}

public Integer getId() {
    return id;
}

public void setId(Integer id) {
    this.id = id;
}


public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}


@Override
public String toString() {
    return name;
}


}

TransactionDetails.java:

@Entity
@Table(name = "TransactionDetail")
public class TransactionDetails {
@Id
@GeneratedValue
@Column(name="ID")
private Integer id;

@Column(name="TransactionID")
private Integer transactionID;

@Column(name="AccountID")
private Integer accountID;

@Column(name="Amount")
private Float amount;

public TransactionDetails() {
    super();
    // TODO Auto-generated constructor stub
}

public TransactionDetails(Integer id, Integer transactionID,
        Integer accountID, Float amount) {
    super();
    this.id = id;
    this.transactionID = transactionID;
    this.accountID = accountID;
    this.amount = amount;
}

public Integer getId() {
    return id;
}

public void setId(Integer id) {
    this.id = id;
}

public Integer getTransactionID() {
    return transactionID;
}

public void setTransactionID(Integer transactionID) {
    this.transactionID = transactionID;
}

public Integer getAccountID() {
    return accountID;
}

public void setAccountID(Integer accountID) {
    this.accountID = accountID;
}


public Float getAmount() {
    return amount;
}

public void setAmount(Float amount) {
    this.amount = amount;
}


}

TransactionHeaders.java:

@Entity
@Table(name = "TransactionHeader")
public class TransactionHeaders {
@Id
@GeneratedValue
@Column(name="ID")
private Integer id;

@Column(name="Date")
private Timestamp date;

public TransactionHeaders() {
    super();
    // TODO Auto-generated constructor stub
}

public TransactionHeaders(Integer id,Timestamp date) {
    super();
    this.id = id;
    this.date = date;
}

public Integer getId() {
    return id;
}

public void setId(Integer id) {
    this.id = id;
}

public Timestamp getDate() {
    return date;
}

public void setDate(Timestamp date) {
    this.date = date;
}


}

Answer 1

要制作带有一些选项的 query，您需要：

Query que;
StringBuilder where = new StringBuilder();
String query = "select h from " + entityClass.getName() + " h ";

加入：

query = query +" [LEFT] JOIN FETCH h.table t ";

添加参数

where.append(" t.field LIKE :attribute");
que.setParameter("attribute", "your_value"));

使用给定的参数创建查询

que = em.createQuery(String.format("%s WHERE %s", query, where));

获取结果

que.getResultList();

Answer 2

如果实体之间没有关系，您可以将其全部放在 where 子句中而不是内部联接。

例如 a inner join TransactionHeader b on a.TransactionID = b.ID 会变成 from <some table> a, <some other table> b where a.TransactionID = b.ID。

更新

对于 select 子句中的条件字段，使用 CASE ... WHEN 语法

Query query=getCurrentSession().createQuery("SELECT A.transactionID, A.id, A.accountID, CASE WHEN A.amount < 0 THEN (A.amount*-1) ELSE A.amount END as Amount, CASE WHEN A.amount < 0 THEN 'Payment' ELSE 'Receipt' END as Type, B.date, C.name from TransactionHeaders B, TransactionDetails A, Accounts C where B.id = A.transactionID and A.accountID = C.id and A.transactionID in (SELECT D.transactionID from TransactionDetails D where D.accountID = :Id)");
query.setParameter("Id", id);

Answer 3

使用当前的实体映射，您必须使用交叉连接（或自然连接）并将连接条件添加为 where 条件，即如下所示：

SELECT <whatever> FROM TransactionHeaders h, TransactionDetails d, Account a 
  WHERE  
    h.TransactionID = d.TransactionID
    AND c.AccountID = d.ID
    AND h.TransactionID IN (SELECT TransactionID from TransactionDetail where AccountID = 56)
    AND c.AccountID != 56

要使用 HQL/JPQL 联接，您必须更改映射以使用实体关系，即多对多等。

顺便说一句，我会研究您的命名方案以遵守约定，即字段将以小写字母开头（例如 transactionID），实体 class 名称应描述单个实体（例如 TransactionHeader 而不是 TransactionHeaders）。

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