jointure.scala

来自「JAVA 语言的函数式编程扩展」· SCALA 代码 · 共 46 行

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2007, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

// $Id:Jointure.scala 6853 2006-03-20 16:58:47 +0100 (Mon, 20 Mar 2006) dubochet $


package scala.dbc.statement


/** A jointure between two relations. */
abstract class Jointure extends Relation {
  
  /** The relation on the left part of the join. */
  def leftRelation: Relation
  
  /** The relation on the right part of the join. */
  def rightRelation: Relation
  
  /** The type of the jointure. */
  def joinType: JoinType
  
  /** The condition on which the jointure needs be done. */
  def joinCondition: Option[Expression]
  
  /** A SQL-99 compliant string representation of the relation statement. */
  def sqlString: String = "SELECT * FROM " + sqlInnerString
  
  /** A SQL-99 compliant string representation of the relation sub-
   *  statement. This only has a meaning inside a query.
   */
  def sqlInnerString: String =
    leftRelation.sqlInnerString + " " +
    joinType.sqlString + " " +
    rightRelation.sqlInnerString +
    (joinCondition match {
      case Some(jc) => jc.sqlString
      case None => ""
    })
  
}