api-docs / org.ktorm.entity / eachSumByTo

eachSumByTo

inline fun <E : Any, T : BaseTable<E>, K : Any, C : Number, M : MutableMap<in K?, in C?>> EntityGrouping<E, T, K>.eachSumByTo(
    destination: M,
    columnSelector: (T) -> ColumnDeclaring<C>
): M

(source code)

Group elements from the source sequence by key and sum the columns or expressions provided by the columnSelector
function for elements in each group, then store the results in the destination map.

The key for each group is provided by the EntityGrouping.keySelector function, and the generated SQL is like:
select key, sum(column) from source group by key.

Parameters

destination - a MutableMap used to store the results.

columnSelector - a function that accepts the source table and returns the column or expression for summing.

Return
the destination map associating the key of each group with the summing result in the group.