油滑：選擇不工作的列

Question

我想簡單地寫一個查詢，它只爲每個結果行取代一列（從...中選擇標題），而不是全部（select * ... from）。我的SQL查詢將是：

select titel from Lied; 

根據http://slick.typesafe.com/doc/3.1.1/sql-to-slick.html?highlight=case#id3我應該能夠通過簡單地做這樣的事情在光滑3.1只選擇幾個列：

people.map(p => (p.age, p.name ++ " (" ++ p.id.asColumnOf[String] ++ ")")).result 

對我來說，這將意味着：

lieds.map(x => (x.titel)).result.map { println } 

這不起作用。 Eclipse說：

No matching Shape found. Slick does not know how to map the given types. Possible causes: T in Table[T] does not match your * projection. Or you use an unsupported type in a Query (e.g. scala List). Required level: slick.lifted.FlatShapeLevel Source type: slick.lifted.Rep[String] Unpacked type: T Packed type: G

我應該如何解決這個問題？我想我還是不能在這裏結合一些基礎知識，儘管讀scala slick method I can not understand so far（不知道這是否仍然適用於光滑3.1）和光滑的3.1文檔。

我的表（從光滑的生成）：

case class LiedRow(id: Long, titel: String, rubrikId: Option[Long] = None, stichwoerter: Option[String] = None, bemerkungen: Option[String] = None, createdAt: Option[java.sql.Timestamp] = None, updatedAt: Option[java.sql.Timestamp] = None, externallink: Option[String] = None, lastedituserId: Long, tonality: Option[String] = None) 

    implicit def GetResultLiedRow(implicit e0: GR[Long], e1: GR[String], e2: GR[Option[Long]], e3: GR[Option[String]], e4: GR[Option[java.sql.Timestamp]]): GR[LiedRow] = GR{ 
    prs => import prs._ 
    LiedRow.tupled((<<[Long], <<[String], <<?[Long], <<?[String], <<?[String], <<?[java.sql.Timestamp], <<?[java.sql.Timestamp], <<?[String], <<[Long], <<?[String])) 
    } 

    class Lied(_tableTag: Tag) extends Table[LiedRow](_tableTag, "lied") { 
    def * = (id, titel, rubrikId, stichwoerter, bemerkungen, createdAt, updatedAt, externallink, lastedituserId, tonality) <> (LiedRow.tupled, LiedRow.unapply) 
    def ? = (Rep.Some(id), Rep.Some(titel), rubrikId, stichwoerter, bemerkungen, createdAt, updatedAt, externallink, Rep.Some(lastedituserId), tonality).shaped.<>({r=>import r._; _1.map(_=> LiedRow.tupled((_1.get, _2.get, _3, _4, _5, _6, _7, _8, _9.get, _10)))}, (_:Any) => throw new Exception("Inserting into ? projection not supported.")) 


    val id: Rep[Long] = column[Long]("id", O.AutoInc, O.PrimaryKey) 
    val titel: Rep[String] = column[String]("Titel") 
    val rubrikId: Rep[Option[Long]] = column[Option[Long]]("rubrik_id", O.Default(None)) 
    val stichwoerter: Rep[Option[String]] = column[Option[String]]("Stichwoerter", O.Default(None)) 
    val bemerkungen: Rep[Option[String]] = column[Option[String]]("Bemerkungen", O.Default(None)) 
    val createdAt: Rep[Option[java.sql.Timestamp]] = column[Option[java.sql.Timestamp]]("created_at", O.Default(None)) 
    val updatedAt: Rep[Option[java.sql.Timestamp]] = column[Option[java.sql.Timestamp]]("updated_at", O.Default(None)) 
    val externallink: Rep[Option[String]] = column[Option[String]]("externalLink", O.Default(None)) 
    val lastedituserId: Rep[Long] = column[Long]("lastEditUser_id") 
    val tonality: Rep[Option[String]] = column[Option[String]]("tonality", O.Length(30,varying=true), O.Default(None)) 

    lazy val rubrikFk = foreignKey("liedRubrik", rubrikId, Rubrik)(r => Rep.Some(r.id), onUpdate=ForeignKeyAction.Cascade, onDelete=ForeignKeyAction.NoAction) 
    lazy val userFk = foreignKey("liedLastEditUser", lastedituserId, User)(r => r.id, onUpdate=ForeignKeyAction.Cascade, onDelete=ForeignKeyAction.NoAction) 
    } 
    lazy val Lied = new TableQuery(tag => new Lied(tag)) 

Answer 1

問題解決了。

我不得不使用

import slick.driver.MySQLDriver.api._ 

代替

import slick.driver.MySQLDriver.api.DBIO 
import slick.driver.MySQLDriver.api.Database 
import slick.driver.MySQLDriver.api.columnExtensionMethods 
import slick.driver.MySQLDriver.api.longColumnType 
import slick.driver.MySQLDriver.api.streamableQueryActionExtensionMethods 
import slick.driver.MySQLDriver.api.valueToConstColumn 

當我和月食不同的查詢玩耍（或我？）最終將上述import語句上我的課，我執行選擇。

正如你可以在我的問題中看到的那樣，即使在其他查詢正在工作時，我也一直會使用「map」一樣的錯誤（請參閱Eclipse error mark）。

但是，用簡單的import slick.driver.MySQLDriver.api._代替那些進口報表解決了我的問題。不知道爲什麼，但現在，我們所有人都期待着。如果您知道me/eclipse添加的導入有問題，請發表評論。

Answer 2

如果你用這個例子：https://github.com/pedrorijo91/play-slick3-steps/blob/master/app/models/User.scala

而是具有：

def get(id: Long): Future[Option[User]] = { 
    dbConfig.db.run(users.filter(_.id === id).result.headOption) 
    } 

您可以使用

只選擇電子郵件字段

def getField(id: Long): Future[Option[String]] = { 
    dbConfig.db.run(users.filter(_.id === id).map(_.email).result.headOption) 
    }