光滑连接两个表并获得两者的结果

Question

我有这样的多对多关系设置:

人< - > PersonField < - >字段

现在,我不仅要查询Person的所有字段(我可以这样做),而且还要查询PersonField与Person of Field的连接版本.(我想在数据透视/中间表"PersonField"中查询/检索信息!)

人:

case class Person(id: Long, name: String)
{
   def fields =
   {
       person <- Persons.all.filter(_.id === this.id)
       field <- person.fields
   } yield field
}

class Persons(tag: Tag) extends Table[Person](tag, "persons")
{
    def id = column[Long]("id", O.PrimaryKey, O.AutoInc)
    def name = column[String]("name")

    def * = (id, name) <> (Person.tupled, Person.unapply)
    def fields = PersonFields.all.filter(_.personID === id).flatMap(_.fieldFK)
}

object Persons
{
    lazy val all = TableQuery[Persons]
}

领域:

case class Field(id: Long, name: String, description: Option[String])

class Fields(tag: Tag) extends Table[Field](tag, "fields")
{
    def id = column[Long]("id", O.PrimaryKey, O.AutoInc)
    def name = column[String]("name")
    def description = column[Option[String]]("description")

    def * = (id, name, description) <> (Field.tupled, Field.unapply)
}

object Fields
{
    lazy val all = TableQuery[Fields]
}

PersonField:

case class PersonField(id: Long, personID: Long, fieldID: Long, value: String)

// TODO add constraint to make (personID, fieldID) unique
class PersonFields(tag: Tag) extends Table[PersonField](tag, "person_field")
{
  def id = column[Long]("id", O.PrimaryKey, O.AutoInc)
  def personID = column[Long]("person_id")
  def fieldID = column[Long]("field_id")
  def value = column[String]("value")

  def * = (id, personID, fieldID, value) <> (PersonField.tupled, PersonField.unapply)

  def personFK = foreignKey("person_fk", personID, Persons.all)(_.id)
  def fieldFK = foreignKey("field_fk", fieldID, Fields.all)(_.id)
}

object PersonFields
{
  lazy val all = TableQuery[PersonFields]
}

现在查询一个Person的所有字段我有一个小帮助类:

def getFields(p: Person): Future[Seq[Field]] =
{
    val query = p.fields
    db.run(query.result)
}

所以我能做到

val personX ...

personX.onSuccess
{
    case p: Person =>
    {
        val fields = helper.getFields(p)
        fields.onSuccess
        {
            case f: Seq[Field] => f foreach println 
        }  
    }
}

现在,personX的每个字段都会打印到控制台.奇迹般有效.

问题是,我也想获得PersonField(使用Field)!

所以我尝试了以下更改(其中一些不起作用,我不记得了)

在人:

def fields =
{
    for
    {
        person <- Persons.all.filter(_.id === this.id)
        field <- person.fields join Fields.all on (_.fieldID === _.id)
    } yield field
}

在人

def fields = PersonFields.all.filter(_.personID === id) //这里没有flatMap!

然后getFields(p:Person)看起来像这样:

def getFields(p: Person): Future[Seq[(PersonField, Field)]]

但

personX.onSuccess
{
    case p: Person =>
    {
        val fields = helper.getFields(p)
        fields.onSuccess
        {
            case f: Seq[(PersonField, Field)] => f map(f => println(f._1)} 
        }  
    }
}

没有给我什么,所以我想我的联系一定是错的.但究竟我做错了什么？

Answer 1

您可以将所有三个连接起来，然后得出结果

\n\n

for {\n      ((personField, person), field) <- PersonFields.all join Persons.all on (_.personId === _.id)\xc2\xa0join Fields.all on (_._1.fieldId === _.id)\n      if person.id === this.id\n    } yield (personField, person, field)\n

\n\n

（我不确定我是否准确地得到了您想要从查询中得到的内容，因此您可以只编辑产量部分）

\n