On 2016-04-13 Daniel Lenski <dlenski@xxxxxxxxx> wrote: > Hi all, > I'm trying to find a straightforward and reliable way to differentiate > positive, negative, and zero time intervals while handling NULL in the > same way as the SIGN() function. I'm not sure that "positive time interval" is a thing. Witness: dakkar=> select interval '1 month - 30 days' > interval '0'; ┌──────────┐ │ ?column? │ ├──────────┤ │ f │ └──────────┘ (1 row) not positive? maybe it's negative? dakkar=> select interval '1 month - 30 days' < interval '0'; ┌──────────┐ │ ?column? │ ├──────────┤ │ f │ └──────────┘ (1 row) no, not negative either. Why? Well… dakkar=> select date '2016-03-01' + interval '1 month - 30 days'; ┌─────────────────────┐ │ ?column? │ ├─────────────────────┤ │ 2016-03-02 00:00:00 │ └─────────────────────┘ (1 row) when used this way, it looks positive, but dakkar=> select date '2016-02-01' + interval '1 month - 30 days'; ┌─────────────────────┐ │ ?column? │ ├─────────────────────┤ │ 2016-01-31 00:00:00 │ └─────────────────────┘ (1 row) when used this way, it looks negative. So I suspect the reason SIGN() is not defined for intervals is that it cannot be made to work in the general case. -- Dakkar - <Mobilis in mobile> GPG public key fingerprint = A071 E618 DD2C 5901 9574 6FE2 40EA 9883 7519 3F88 key id = 0x75193F88 Thrashing is just virtual crashing.
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