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In one-to-many, how to express “where is” in a spot?

Suppose two tables:

  • cats, Cat

  • personality traits, Personality_Trait

were Cat

has id

, and Personality_Trait

has a id

string trait

.

eg.

== Cat ==
id  |  name
---------------
0   |  Tom
1   |  Garfield
2   |  Kitty

== Personality_Trait ===
id  |  trait
---------------
0   |  stubborn
1   |  stubborn
1   |  sleepy
1   |  moody
2   |  sleepy
2   |  moody

How do I get all cats that have at least all the traits that interest me?

eg. how do i get Garfield

when i search stubborn

andmoody

I was thinking something like

Personality_Trait.groupBy(_.id).filter {
  case (id, traits) => <predicate on traits>
}.map(_._1)
+3


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2 answers


I found a solution, albeit inelegant and potentially ineffective:



val desiredTraits = Set("stubborn", "moody")

(for {
  catId <- Personality_Trait.filter(_.trait inSetBind desiredTraits)
             .groupBy(_.id).map { case (txnId, foundTraits) =>
               (txnId, foundTraits.length)
             }.filter { case (txnId, foundTraitCount) =>
               foundTraitCount >= desiredTraits.size
             }.map(_._1)
  cat <- Cat if cat.id === catId
} yield (cat)).result
0


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I think first, you should translate Personality_Trait from (id, trait) to tempRecord (id, seq [trait]) and then predicate on that.



-1


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