chickadee » sql-de-lite » fold-rows*

fold-rows kons knilprocedure
fold-rows* kons knilprocedure

Calls (kons x xs) once for each row, where x is the current row data and xs is the seed (previous return value from kons). The initial seed is knil.

(query (fold-rows cons '()) s)
; => ((2 "baz" "quux") (1 "foo" "bar"))
;; sum the returned rowids
(query (fold-rows (lambda (x xs) (+ (car x) xs))
; => 3
;; that was contrived, you should actually do the sum in the database
(car (query fetch (sql db "select sum(rowid) from mytable;")))
; => 3

fold-rows* behaves like fold-rows, but the kons callback is invoked with one column for each argument value, plus the seed as the last argument -- for example, as (kons x y z seed). This turns out to be quite inefficient and makes little sense, so fold-rows* is deprecated as of 0.4.2.