From: Achilleas Mantzios <achill@matrix.gatewaynet.com>
To: pgsql-sql@postgresql.org
Subject: Re: can someone explain confusing array indexing nomenclature
Date: Tue, 20 Feb 2007 09:42:17 +0200
Message-ID: <200702200942.18500.achill@matrix.gatewaynet.com> (raw)
In-Reply-To: <9009934.post@talk.nabble.com>
References: <8971770.post@talk.nabble.com>
<200702161034.43399.achill@matrix.gatewaynet.com>
<9009934.post@talk.nabble.com>
Στις Παρασκευή 16 Φεβρουάριος 2007 20:35, ο/η chrisj έγραψε:
> I am quite sure the [2] is not discarded, easy enough to test but I don't
> have access to PG at the moment.
Well it should, since
dynacom=# SELECT
(CAST( '{{meeting,lunch},{training,presentation}}' as text[][]))[1:1];
text
-------------------
{{meeting,lunch}}
(1 row)
dynacom=# SELECT
(CAST( '{{meeting,lunch},{training,presentation}}' as text[][]))[1:1][1];
text
-------------
{{meeting}}
(1 row)
dynacom=# SELECT
(CAST( '{{meeting,lunch},{training,presentation}}' as text[][]))[1:1][2];
text
-------------------
{{meeting,lunch}}
(1 row)
dynacom=# SELECT
(CAST( '{{meeting,lunch},{training,presentation}}' as text[][]))[1:1][3];
text
-------------------
{{meeting,lunch}}
(1 row)
dynacom=# SELECT
(CAST( '{{meeting,lunch},{training,presentation}}' as text[][]))[1:1][1000];
text
-------------------
{{meeting,lunch}}
(1 row)
dynacom=#
>
> Achilleas Mantzios wrote:
> > Στις Πέμπτη 15 Φεβρουάριος 2007 18:55, ο/η chrisj έγραψε:
> >> 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.
> >
> > Now that i think about it again, i speculate that the [2] is discarded.
> >
> >> - chris
> >>
> >> Achilleas Mantzios wrote:
> >> > Ξ£ΟΞΉΟ Ξ�Ξ΅ΟΞ¬ΟΟΞ· 14 ΦΡβΟΞΏΟ Ξ¬ΟΞΉΞΏΟ 2007 21:31, ΞΏ/Ξ·
> >>
> >> chrisj
> >
> > ΞΞ³ΟΞ±ΟΞ΅:
> >> >> given the following table:
> >> >>
> >> >> protocal2=> 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=> SELECT schedule[1][2] FROM sal_emp WHERE name = 'Bill';
> >> >> schedule
> >> >> ----------
> >> >> lunch
> >> >> (1 row)
> >> >>
> >> >> protocal2=> SELECT schedule[1:1][2] FROM sal_emp WHERE name = 'Bill';
> >> >> schedule
> >> >> -------------------
> >> >> {{meeting,lunch}}
> >> >> (1 row)
> >> >
> >> > 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,
> >> > 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
> >> > SELECT schedule[1:1][888] FROM sal_emp WHERE name = '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.
> >> > --
> >> > Achilleas Mantzios
> >> >
> >> > ---------------------------(end of
> >>
> >> broadcast)---------------------------
> >>
> >> > TIP 3: Have you checked our extensive FAQ?
> >> >
> >> > http://www.postgresql.org/docs/faq
> >
> > --
> > Achilleas Mantzios
> >
> > ---------------------------(end of broadcast)---------------------------
> > TIP 3: Have you checked our extensive FAQ?
> >
> > http://www.postgresql.org/docs/faq
--
Achilleas Mantzios
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Cc: achill@matrix.gatewaynet.com
Subject: Re: can someone explain confusing array indexing nomenclature
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