chickadee » postgresql » column-fold

column-fold KONS KNIL RESULTprocedure
column-fold* KONS KNIL RESULTprocedure

As row-fold/row-fold*, except this iterates sideways through the columns instead of lengthways through the columns, calling KONS with all values in all the rows of the current column, from left to right.

The starred version is much less useful here since you often don't know the number of returned columns, but it is provided for consistency.

(import postgresql)

(let ((conn (connect '((dbname . test)))))
   (column-fold (lambda (col sum) (+ (car col) sum))
                (query conn "SELECT 1, 100 UNION SELECT 2, 200")))
 => 101