scala - 如何在 slick 中进行连接？

Question

我有 2 个查询，并且想做一个像 sql 这样的连接

例如，我有这些表..

object Family extends Table[Long]("Family") {
  def id = column[Long]("id")
  def * = id
}

object Person extends Table[(Long, Long)]("Person") {
  def id = column[Long]("id")
  def FamilyId = column[Long]("FamilyId")
  def * = id ~ FamilyId ~ size
}

Answer 1

val implicitInnerJoin = for {
  c <- Family
  s <- Person if c.id === s.FamilyId
} yield (c.id, s.id)

Answer 2

来自 Slick 文档：http ://slick.typesafe.com/doc/1.0.0/lifted-embedding.html#joining-and-zipping ，以下是 Slick 中的一些可能连接以及与之相关的一些粗略 SQL

val implicitCrossJoin = for {
  c <- Coffees
  s <- Suppliers
} yield (c.name, s.name)

//SELECT c.name, s.name FROM Coffees c, Suppliers s


val implicitInnerJoin = for {
  c <- Coffees
  s <- Suppliers if c.supID === s.id
} yield (c.name, s.name)
//SELECT c.name, s.name FROM Coffees c, Suppliers s where c.supID = s.id    

val explicitCrossJoin = for {
  (c, s) <- Coffees innerJoin Suppliers
} yield (c.name, s.name)
//SELECT c.name, s.name FROM Coffees c CROSS JOIN Suppliers s    

val explicitInnerJoin = for {
  (c, s) <- Coffees innerJoin Suppliers on (_.supID === _.id)
} yield (c.name, s.name)
//SELECT c.name, s.name FROM Coffees c INNER JOIN Suppliers s ON (c.supID = s.id)   

val explicitLeftOuterJoin = for {
  (c, s) <- Coffees leftJoin Suppliers on (_.supID === _.id)
} yield (c.name, s.name.?)
//SELECT c.name, s.name FROM Coffees c LEFT OUTER JOIN Suppliers s ON (c.supID = s.id)

val explicitRightOuterJoin = for {
  (c, s) <- Coffees rightJoin Suppliers on (_.supID === _.id)
} yield (c.name.?, s.name)
//SELECT c.name, s.name FROM Coffees c RIGHT OUTER JOIN Suppliers s ON (c.supID = s.id)

val explicitFullOuterJoin = for {
  (c, s) <- Coffees outerJoin Suppliers on (_.supID === _.id)
} yield (c.name.?, s.name.?)
//SELECT c.name, s.name FROM Coffees c FULL OUTER JOIN Suppliers s ON (c.supID = s.id)

如您所见，大多数构造都非常直接地映射到 SQL。

希望有帮助

Answer 3

这是 Slick 3.x 的更新答案：

val families = TableQuery[Family]
val people = TableQuery[Person]

val familyJoinQuery = for {
  family <- families
  person <- people if family.id === person.FamilyId
} yield (family, person)

或者，并且很少记录，您还可以执行以下操作：

val familyJoinQuery = families.join(people).on((family, person) => family.id === person.FamilyId)