Scala Slick:如何执行except join (带有is null的左外join )？

import slick.jdbc.MySQLProfile.api._

// 定义表结构
class TableA(tag: Tag) extends Table[(Int, Option[String])](tag, "table_a") {
  def id = column[Int]("id", O.PrimaryKey)
  def name = column[Option[String]]("name")
  def * = (id, name)
}

class TableB(tag: Tag) extends Table[(Int, Option[String])](tag, "table_b") {
  def id = column[Int]("id", O.PrimaryKey)
  def name = column[Option[String]]("name")
  def * = (id, name)
}

// 创建表对象
val tableA = TableQuery[TableA]
val tableB = TableQuery[TableB]

// 执行查询
val query = for {
  (a, b) <- tableA joinLeft tableB on (_.id === _.id) if b.map(_.name).isDefined
} yield (a, b)

val result = db.run(query.result)