Message-ID: <8989242.post@talk.nabble.com>
Date: Thu, 15 Feb 2007 08:55:58 -0800 (PST)
From: chrisj <chrisj.wood@sympatico.ca>
To: pgsql-sql@postgresql.org
Subject: Re: can someone explain confusing array indexing nomenclature
In-Reply-To: <200702151224.12455.achill@matrix.gatewaynet.com>
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References: <8971770.post@talk.nabble.com>
	<200702151224.12455.achill@matrix.gatewaynet.com>


Thanks Achilleas,

I see what you are saying, but if we consider just the index "[2]" for a
moment,
it means something different depending upon the context  (in one case it
means "2" and in the other case it means "1:2") and the context is
determined by the format of indexes on other dimensions.

I believe I understand....but incredibly confusing.

- chris


Achilleas Mantzios wrote:
>=20
> =CE=A3=CF=84=CE=B9=CF=82 =CE=A4=CE=B5=CF=84=CE=AC=CF=81=CF=84=CE=B7 14 =
=CE=A6=CE=B5=CE=B2=CF=81=CE=BF=CF=85=CE=AC=CF=81=CE=B9=CE=BF=CF=82 2007 21:=
31, =CE=BF/=CE=B7 chrisj =CE=AD=CE=B3=CF=81=CE=B1=CF=88=CE=B5:
>> given the following table:
>>
>> protocal2=3D> select * from sal_emp ;
>>  name  |      pay_by_quarter       |                 schedule
>> -------+---------------------------+------------------------------------=
---
>>---- Bill  | {10000,10000,10000,10000} |
>> {{meeting,lunch},{training,presentation}}
>>  Carol | {20000,25000,25000,25000} |
>> {{breakfast,consulting},{meeting,lunch}}
>> (2 rows)
>>
>> why do the following two queries yield different results??
>>
>> protocal2=3D> SELECT schedule[1][2] FROM sal_emp WHERE name =3D 'Bill';
>>  schedule
>> ----------
>>  lunch
>> (1 row)
>>
>> protocal2=3D> SELECT schedule[1:1][2] FROM sal_emp WHERE name =3D 'Bill'=
;
>>      schedule
>> -------------------
>>  {{meeting,lunch}}
>> (1 row)
>=20
> The [n:m] notation denotes a slice of the array (not element).
> So schedule[1][2] is the Array element on 2nd col of 1st row,=20
> while schedule[1:1][2] could mean
> the second row of the subarray schedule[1:1][1:2].
> So these two are foundamentally different things.
> In my 7.4 even if you gave=20
> SELECT schedule[1:1][888] FROM sal_emp WHERE name =3D 'Bill';
> you would still get  {{meeting,lunch}} as a result.
> (Right or wrong is another story).
> Anyway the first time you query for a "text",
> the second time you query for a "text[]", so you should expect
> different results.
> --=20
> Achilleas Mantzios
>=20
> ---------------------------(end of broadcast)---------------------------
> TIP 3: Have you checked our extensive FAQ?
>=20
>                http://www.postgresql.org/docs/faq
>=20
>=20

--=20
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