I have a trigger function problem that threatens to cause my early demise. Please someone help an absolute novice.
I have two tables, invoice and invline, with the usual functions.
Table invoice has a column for the total of debit lines, and a column for the total of credit (payment) lines. The function is triggered by any change in inv.gross
The ERROR occurs if there are no invline found by either summing part, where we set dr_total or cr_total.
If I change "sum" to "count" it works as expected, returning 0.00
--THE FUNCTION
UPDATE invoice SET
invoice.cr_total = (
SELECT
sum(invline.gross)
FROM invline
WHERE invline.type > 4 AND invline.invoice_id = 200003
)
,
invoice.dr_total = (
SELECT
sum(invline.gross)
FROM invline
WHERE invline.type <5 AND invline.invoice_id = 200003
ERROR: null value in column "po_cr_total" violates not-null constraint
Anyone?
Mike
There is a difference between the behaviour of sum and count. Count returns the number of found records(0 in this case) while sum returns the sum of the given expression from the found records. And anything plus null is always null in Postgres.
However you can use the coalesce function which returns its first non-null argument to ensure a non null result.
SELECT
coalece(sum(invline.gross), 0)
FROM invline
WHERE invline.type > 4 AND invline.invoice_id = 200003
or
invoice.cr_total = coalesce((SELECT
sum(invline.gross)
FROM invline
WHERE invline.type > 4 AND invline.invoice_id = 200003),0)
