如何使用Play框架从Scala中的Mysql获取结果的总和？

Question

我正在使用简单的Scala Web应用程序，并且正在运行查询，然后Play应用程序出现异常

[RuntimeException：UnexpectedNullableFound（ColumnName（.SUM（score），Some（SUM（score））））]]

play.api.Application$$anon$1: Execution exception[[RuntimeException: UnexpectedNullableFound(ColumnName(.SUM(score),Some(SUM(score))))]]
    at play.api.Application$class.handleError(Application.scala:289) ~[play_2.10.jar:2.1.2]
    at play.api.DefaultApplication.handleError(Application.scala:383) ~[play_2.10.jar:2.1.2]
    at play.core.server.netty.PlayDefaultUpstreamHandler$$anonfun$18$$anonfun$apply$18.apply(PlayDefaultUpstreamHandler.scala:310) ~[play_2.10.jar:2.1.2]
    at play.core.server.netty.PlayDefaultUpstreamHandler$$anonfun$18$$anonfun$apply$18.apply(PlayDefaultUpstreamHandler.scala:308) ~[play_2.10.jar:2.1.2]
    at play.api.libs.concurrent.PlayPromise$$anonfun$extend1$1.apply(Promise.scala:113) ~[play_2.10.jar:2.1.2]
    at play.api.libs.concurrent.PlayPromise$$anonfun$extend1$1.apply(Promise.scala:113) ~[play_2.10.jar:2.1.2]
Caused by: java.lang.RuntimeException: UnexpectedNullableFound(ColumnName(.SUM(score),Some(SUM(score))))
    at scala.sys.package$.error(package.scala:27) ~[scala-library.jar:na]
    at anorm.Sql$.as(Anorm.scala:535) ~[anorm_2.10.jar:2.1.2]
    at anorm.Sql$class.as(Anorm.scala:453) ~[anorm_2.10.jar:2.1.2]
    at anorm.SimpleSql.as(Anorm.scala:370) ~[anorm_2.10.jar:2.1.2]
    at models.Keyword$$anonfun$getBlogScore$1.apply(Keyword.scala:53) ~[na:na]
    at models.Keyword$$anonfun$getBlogScore$1.apply(Keyword.scala:52) ~[na:na]

型号/关键字.scala

def getBlogScore(word: String, blog: String): Long={DB.withConnection{implicit c=>
 SQL("select SUM(score) from keyword where blog like {blog} and word = {word}").on('blog->blog,'word->word).as(scalar[Long].single)
}
}

我想基于某些条件获取分数列的总和。

给我一些解决此异常的想法！

Answer 1

尝试：

SQL("select SUM(score) from keyword where blog like {blog} and word = {word}").
  on('blog->blog,'word->word).
  as(scalar[Option[Long]].single).
  getOrElse(0L)

Answer 2

我猜当没有行匹配时SUM返回NULL 。 我还猜测在这种情况下，您可能想要0 。

因此，您必须处理这种情况。 Option浮现在脑海。 快速浏览一下文档，对Option进行.singleOpt表示有一个.singleOpt 。

因此，您可以尝试：

def getBlogScore(word: String, blog: String): Long = 
  DB.withConnection { implicit c =>
    SQL("select SUM(score) from keyword where blog like {blog} and word = {word}").
      on('blog->blog,'word->word).
      as(scalar[Long].singleOpt).
      getOrElse(0L)
  }

Answer 3

有点晚了，但是这个问题在Anorm master分支中得到了解决： https : //github.com/playframework/playframework/pull/2072