Question

假设我们有一个包含两个表的数据库：Coffee和Suppliers，我们有相应的案例类和表，就像在文档中一样：

import scala.slick.driver.MySQLDriver.simple._
import scala.slick.lifted.{ProvenShape, ForeignKeyQuery}


// A Suppliers table with 6 columns: id, name, street, city, state, zip
class Suppliers(tag: Tag) extends Table[(Int, String, String, String, String, String)](tag, "SUPPLIERS") {
  def id: Column[Int] = column[Int]("SUP_ID", O.PrimaryKey) // This is the primary key column
  def name: Column[String] = column[String]("SUP_NAME")
  def street: Column[String] = column[String]("STREET")
  def city: Column[String] = column[String]("CITY")
  def state: Column[String] = column[String]("STATE")
  def zip: Column[String] = column[String]("ZIP")

  // Every table needs a * projection with the same type as the table's type parameter
  def * : ProvenShape[(Int, String, String, String, String, String)] = (id, name, street, city, state, zip)
}

// A Coffees table with 5 columns: name, supplier id, price, sales, total
class Coffees(tag: Tag) extends Table[(String, Int, Double, Int, Int)](tag, "COFFEES") {
  def name: Column[String] = column[String]("COF_NAME", O.PrimaryKey)
  def supID: Column[Int] = column[Int]("SUP_ID")
  def price: Column[Double] = column[Double]("PRICE")
  def sales: Column[Int] = column[Int]("SALES")
  def total: Column[Int] = column[Int]("TOTAL")

  def * : ProvenShape[(String, Int, Double, Int, Int)] = (name, supID, price, sales, total)

  // A reified foreign key relation that can be navigated to create a join
  def supplier: ForeignKeyQuery[Suppliers, (Int, String, String, String, String, String)] = 
    foreignKey("SUP_FK", supID, TableQuery[Suppliers])(_.id)
}

现在假设我们想要加入：

   val result = for {
       c <- coffees
       s <- suppliers if c.supID === s.id
} yield (c.name, s.name)

这里处理结果很复杂（如果我们有很多连接则会更复杂），因为我们需要始终记住名称的顺序，知道_._1或_._2是什么到...等。

问题1 有没有办法将结果类型更改为包含所需列的新类的表？

问题2 这是一种方法，但我无法完成它，我们构建一个案例类，例如：

case class Joined(nameS: String,nameC: String)

然后我们构建了相应的表格，我不知道如何

class Joineds extends Table[Joinedclass] {
//Todo
}

当我们编写连接时，我们可以编写类似的东西（这样我们就可以将结果转换为连接类型）：

   val result = for {
       c <- coffees
       s <- suppliers if c.supID === s.id
} yield (c.name, s.name).as(Joinds)

谢谢。

Answer 1

你可以定义它：

val result = for {
  c <- coffees
  s <- suppliers if c.supID === s.id
} yield Joined(c.name, s.name)

把它塞进一个方便的地方？

为一个不存在的表格slick scala创建一个类表（Slick 3.0.0，scala）

1 个答案: