groupingBy
fun <E : Any, T : BaseTable<E>, K : Any> EntitySequence<E, T>.groupingBy(keySelector: (T) -> ColumnDeclaring<K>): EntityGrouping<E, T, K>(source)
Create an EntityGrouping from the sequence to be used later with one of group-and-fold operations.
The keySelector can be applied to each record to get its key, or used as the group by clause of generated SQLs.
The operation is intermediate.
