Scala Slick 3.1 多重连接

Question

我正在尝试在 Slick 3.1.1 中执行多个连接。我想达到的结果是这样的:

SELECT * FROM customer LEFT JOIN customer_address ON customer.id = customer_address.customer_id LEFT JOIN address ON customer_address.address_id = address.id

我尝试了以下方法:

val query = for {
  c <- Customer
  ca <- CustomerAddress if ca.customerId === c.id
  a <- Address if a.id === ca.addressId
} yield (c, a)

这里的问题是，如果客户没有地址，它就不会出现，这是有道理的。

然后我尝试了这个:

    val query2 = for {
       (c, ca, a) <- (Customer joinLeft CustomerAddress on (_.id === _.customerId)) joinLeft Address on (_._2.addressId === _.id)
    } yield (c, a)

这里的问题是我在 _._2.addressId 上遇到错误因为 _._2是 Rep目的。

确切的错误:

Error:(21, 110) value addressId is not a member of slick.lifted.Rep[Option[Models.Tables.CustomerAddress]]
  (c, ca, a) <- (Customer joinLeft CustomerAddress on (_.id === _.customerId)) joinLeft Address on (_._2.addressId === _.id)

自动生成的 Slick Tables 类:
http://pastebin.com/e4M3cGU8

如何使用 Slick 获得我想要的结果？

Answer 1

您还需要做的是映射结果。

val query2 = for {
      ((c, ca), a) <- (Customer joinLeft CustomerAddress on (_.id === _.customerId)) joinLeft Address on (_._2.map(_.addressId) === _.id)
} yield (c, a)