Scala Slick过滤器，条件超过两个左连接表

Question

我试图在Slick中重现此查询。

SELECT *
FROM A
JOIN LEFT B AS B1 ON B1.aId = A.id && B1.condition = 'b1'
JOIN LEFT B AS B2 ON B2.aId = A.id && B2.condition = 'b2'

- (no condition, the query in a plain way)

- WHERE B1.status = 'delete' OR B2.status = 'delete'

- WHERE ((B1.status = 'read' AND B2.status <> 'delete') OR (B1.status <> 'delete' AND B2.status = 'read')

- WHERE B1.status = 'write' AND B2.status = 'write'

- WHERE B1.status = 'full' AND B2.status = 'full'

- WHERE ((B1.status = 'full' AND B2.status = 'write') OR (B1.status = 'write' AND B2.status = 'full')

我不确定这是否可行

到目前为止，我有类似的东西

val query = for { ((a, b1Opt), b2Opt) <- ATable.aQuery join
  BTable.BQuery on ((joinTable, bTable) => join._1.id === _.AId && bTable.condition === "b1") join
  BTable.BQuery on ((joinTable, bTable) => join._1.id === _.AId && bTable.condition === "b2")
} yield (a, b1Opt, b2Opt)

而我正在尝试这样的事情

val filterB = query {
  case (a, b1Opt, b2Opt) => {
    bStatus match {
      case "delete" => b1Opt.map(b1 => b1.status === "delete") || b1Opt.map(b2 => b2.status === "delete")
    }

  }
}

Answer 1

根据你所描述的，表A的left join上的表B的两个连续ids应转换为类似于以下内容：

val joinQuery = for {
  ((a, b1), b2) <- tableA joinLeft tableB on ( (x, y) =>
                            x.id === y.aId && y.condition === "b1" )
                          joinLeft tableB on ( (x, y) =>
                            x._1.id = y.aId && y.condition === "b2" )
} yield (a, b1, b2)

而where的B1.status = 'delete' and B2.status = 'delete'条件应如下所示：

val filterB = joinQuery.filter{ case (_, b1, b2) =>
  b1.filter(_.status === "delete").isDefined && b2.filter(_.status === "delete").isDefined
}

请注意，使用left joins，b1和b2包裹在Option中，因此使用isDefined进行and操作。

另外需要注意的是，在执行Bs之前，可能值得考虑使用B.condition = 'b?'将表B1过滤到减少的B2和left join。