In these examples ( https://github.com/szeiger/scala-query/wiki/Queries) foreach (via for comprehension) is used on a scalaquery Query.
But foreach doesn't seem to be present in Query, but only in UnitInvoker.
Where is the implicit conversion comming from that converts from Query to UnitInvoker?
Short answer: from the BasicImplicitConversions trait.
Usually with ScalaQuery you'll bring these conversions into scope by importing the contents of the Implicit field of the profile for your driver:
import org.scalaquery.ql.extended.H2Driver.Implicit._