Re: [SQL] can someone explain confusing array indexing nomenclature

[chrisj]

I am quite sure the [2] is not discarded, easy enough to test but I don't
have access to PG at the moment.


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:
>> > Στις Ξ�Ρτάρτη 14 ΦΡβρουάριος 2007 21:31, ΞΏ/Ξ·
>> chrisj 
> έγραψΡ:
>> >> 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
>> >
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>> >
>> >                http://www.postgresql.org/docs/faq
> 
> -- 
> Achilleas Mantzios
> 
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> 

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