嗨，我下面有两个实体表，其中贷款是我的父类和ddl表类是子类。联接是自定义联接。我还有其他子表可以正确连接。但是对于这个ddl表，我想尝试一个自定义连接。我不知道怎样才能做到。下面是我试图实现的oracle查询。我该怎么做。如果这不是正确的方法，欢迎提出建议。
oracle查询

select dt.DESCRIPTION 
from LOANS l,ddl_table dt
where
        dt.table_name='master' and dt.field_name='mc'
        and  SUBSTR(dt.DESCRIPTION, 2, 1) = l.MC_TYPE
        and l.LOAN_ID = :LOAN_ID

父实体

@DynamicUpdate
@Data
@NoArgsConstructor
@ToString
@Table(name = "LOANS")
@Entity
public class Loans {

@Id
@Column(name = "LOAN_ID")
private Long loanId;

@OneToOne(cascade = CascadeType.ALL)
@WhereJoinTable(clause = "table_name='master' and field_name='type'")
private DDLTable  ddlTable;
// Other child tables.
}

ddl表实体

@Data
@AllArgsConstructor
@NoArgsConstructor
@ToString
@Table(name = "DDL_TABLE")
@Entity
public class DDLTable {

@Id
@Column(name = "TABLE_NAME")
private String tableName;
@Id
@Column(name = "FIELD_NAME")
private String fieldName;

@Column(name = "DESCRIPTION")
private String description;

@Column(name = "FILTER_TYPE")
private String filterType;

}