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我认为下面的代码大多不言自明，但这里有一个简短的解释。

我有一个需要添加到查询条件的 id 列表。我可以轻松地将条件“和”到查询中（见val incorrect下文），但在想出一个“或”条件的好方法时遇到了麻烦。

id 列表不是静态的，我只是在其中放一些作为示例。如果可能的话，我想知道如何使用 for 理解而不使用 for 理解。

此外，如果您想运行代码，您应该能够将此代码放入 repl 并添加一些导入。

object Tbl1Table {

  case class Tbl1(id:Int, gid: Int, item: Int)

  class Tbl1Table(tag:Tag) extends Table[Tbl1](tag, "TBL1") {
    val id = column[Int]("id")
    val gid = column[Int]("gid")
    val item = column[Int]("item")

    def * = (id, gid, item) <> (Tbl1.tupled, Tbl1.unapply)
  }
  lazy val theTable = new TableQuery(tag => new Tbl1Table(tag))

  val ids = List((204, 11), (204, 12), (204, 13), (205, 19))

  val query = for {
    x <- theTable
  } yield x

  println(s"select is ${query.selectStatement}")
  //prints: select is select x2."id", x2."gid", x2."item" from "TBL1" x2

  val idsGrp = ids.groupBy(_._1)
  val incorrect = idsGrp.foldLeft(query)((b, a) =>
    b.filter(r => (r.gid is a._1) && (r.item inSet(a._2.map(_._2))))
  )

  println(s"select is ${incorrect.selectStatement}")
  //prints: select is select x2."id", x2."gid", x2."item" from "TBL1" x2
  //        where ((x2."gid" = 205) and (x2."item" in (19))) and
  //              ((x2."gid" = 204) and (x2."item" in (11, 12, 13)))

  //but want to "or" everything, ie:
  //prints: select is select x2."id", x2."gid", x2."item" from "TBL1" x2
  //        where ((x2."gid" = 205) and (x2."item" in (19))) or
  //              ((x2."gid" = 204) and (x2."item" in (11, 12, 13)))
}
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1 回答 1

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这似乎工作正常：

import scala.slick.driver.PostgresDriver.simple._

case class Tbl1Row(id:Int, gid: Int, item: Int)

class Tbl1Table(tag:Tag) extends Table[Tbl1Row](tag, "TBL1") {
  val id = column[Int]("id")
  val gid = column[Int]("gid")
  val item = column[Int]("item")

  def * = (id, gid, item) <> (Tbl1Row.tupled, Tbl1Row.unapply)
}

lazy val theTable = new TableQuery(tag => new Tbl1Table(tag))

val ids = List((204, 11), (204, 12), (204, 13), (205, 19))
val idsGrp = ids.groupBy(_._1)
val correct = theTable.filter(r => idsGrp.map(t => (r.gid is t._1) && (r.item inSet(t._2.map(_._2)))).reduce(_ || _))
println(s"select is ${correct.selectStatement}")

输出是

select is select s16."id", s16."gid", s16."item" from "TBL1" s16 where ((s16."gid" = 205) and (s16."item" in (19))) or ((s16."gid" = 204) and (s16."item" in (11, 12, 13)))
于 2014-07-17T14:08:02.723 回答