Re: Relation subset operators
From: Walter Mitty <wamitty_at_verizon.net>
Date: Sat, 06 Jun 2009 14:16:13 GMT
Message-ID: <NSuWl.939$u86.798_at_nwrddc01.gnilink.net>
> Thanks. Good observations, one could say such queries are indeed
> subjunctive (maybe all queries are), here's Date's SQL for "Get suppliers
> who supply all purple parts":
> SELECT DISTINCT s.*
> FROM S AS s
> WHERE NOT EXISTS
> ( SELECT DISTINCT p.*
> FROM P AS p
> WHERE p.COLOR = 'Purple'
> AND NOT EXISTS
> ( SELECT DISTINCT sp.*
> FROM SP AS p
> WHERE s.S# = sp.S#
> AND sp.P# = p.P# ) ).
> If I'm not mistaken the answer is that all suppliers supply no purple
> parts. Just a consequence of FOPC.
>
> You might've hit the nail on the head (which the SQL accomplishes rather
> extravagantly by using a wrench instead of a hammer). They did that joke
> in a Marlene Dietrich movie, cafe scene where the guy hustling her and the
> (French) waiter can't take their eyes off her. Hustler asks for coffee
> with no cream. Waiter says there is no cream, would coffee with no milk
> do? So the coffee was the same, no matter whether it had no cream or no
> milk. Perhaps a viewpoint that life is subjunctive is the first baby step
> for escape from mysticism..
Date: Sat, 06 Jun 2009 14:16:13 GMT
Message-ID: <NSuWl.939$u86.798_at_nwrddc01.gnilink.net>
"paul c" <toledobythesea_at_oohay.ac> wrote in message
news:altWl.29656$Db2.6372_at_edtnps83...
> Walter Mitty wrote:
> ...
>> Here's an attempt in Spanish >> >> "Si el conjunto de autos morados fuese un conjunto vacío, >> entonces ningun vendedor no podría vender auto morado alguno >> (nisiquiera uno) de tal modo que todos los vendedores >> los han vendido todos. " >> >> It sounds equally absurd to me. I'm not sure it's right. >> Note the double negative, and the use of a subjunctive. >> ... >
> Thanks. Good observations, one could say such queries are indeed
> subjunctive (maybe all queries are), here's Date's SQL for "Get suppliers
> who supply all purple parts":
>
> SELECT DISTINCT s.*
> FROM S AS s
> WHERE NOT EXISTS
> ( SELECT DISTINCT p.*
> FROM P AS p
> WHERE p.COLOR = 'Purple'
> AND NOT EXISTS
> ( SELECT DISTINCT sp.*
> FROM SP AS p
> WHERE s.S# = sp.S#
> AND sp.P# = p.P# ) ).
>
> If I'm not mistaken the answer is that all suppliers supply no purple
> parts. Just a consequence of FOPC.
>
Once in a while, I try to posit a subjunctive query to SQL. Often, the
response I get is "UNKNOWN".
Then I try to explain, carefully and methodically, that the the answer I'm
looking for is not "UNKNOWN".
SQL dutifully evaluates "NOT UNKNOWN" and responds with "UNKNOWN".
Facts are stubborn things. But, if SQL is to be believed, the absence of facts is even more stubborn yet!
>> A guy walks into a coffee shop, and orders a coffee without cream. >> The server says, "we're all out of cream today." >> "In that case," the guy responds, "I'll have a cup of coffee without >> milk." >> >
> You might've hit the nail on the head (which the SQL accomplishes rather
> extravagantly by using a wrench instead of a hammer). They did that joke
> in a Marlene Dietrich movie, cafe scene where the guy hustling her and the
> (French) waiter can't take their eyes off her. Hustler asks for coffee
> with no cream. Waiter says there is no cream, would coffee with no milk
> do? So the coffee was the same, no matter whether it had no cream or no
> milk. Perhaps a viewpoint that life is subjunctive is the first baby step
> for escape from mysticism..
What difference would it make if life were subjunctive? Received on Sat Jun 06 2009 - 16:16:13 CEST