Обсуждение: how to generate a list of distinct scalar values from a column which type is array

Dear all, <br /><br />given a column which type is for instance varchar(20)[], is there any SQL command that let me
generatethe list of distinct scalar values? <br /><br /><br />e.g.: <br />             col1<br />row 1: (aaa, bb, c)
<br/>row 2: (dddd, eeee) <br />row 3: (aaa, eeee) <br /><br />the query should return: <br /><br />aaa <br />bb <br />c
<br/>dddd <br />eeee <br /><br />if not, I guess the approach is to use stored procedure. Any code
snippet/suggestion?<br/><br />Thanks, Sergio <br /><br /> 

am  Wed, dem 21.02.2007, um 19:21:09 +0100 mailte Sergio Andreozzi folgendes:
> Dear all,
> 
> given a column which type is for instance varchar(20)[], is there any SQL
> command that let me generate the list of distinct scalar values?
> 
> 
> e.g.:
>              col1
> row 1: (aaa, bb, c)
> row 2: (dddd, eeee)
> row 3: (aaa, eeee)
> 
> the query should return:
> 
> aaa
> bb
> c
> dddd
> eeee
> 
> if not, I guess the approach is to use stored procedure. Any code snippet/
> suggestion?

You can, for each row, split the array into the elements with a loop
over array_lower, array_upper, returns this element. Yes, this is a
setof-function. Than you can do a simple select distinct * from
your_function.


I hope this may help you.


Andreas
-- 
Andreas Kretschmer
Kontakt:  Heynitz: 035242/47150,   D1: 0160/7141639 (mehr: -> Header)
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am  Wed, dem 21.02.2007, um 19:21:09 +0100 mailte Sergio Andreozzi folgendes:
> Dear all,
> 
> given a column which type is for instance varchar(20)[], is there any SQL
> command that let me generate the list of distinct scalar values?
> 
> 
> e.g.:
>              col1
> row 1: (aaa, bb, c)
> row 2: (dddd, eeee)
> row 3: (aaa, eeee)
> 
> the query should return:
> 
> aaa
> bb
> c
> dddd
> eeee

Okay, next solution:

test=*# select * from a;     c
-------------{aaa,bb,c}{dddd,eeee}{aaa,eeee}
(3 rows)


test=*# select distinct c[s] from a,  generate_series(1,3)s where c[s] is not null; c
------aaabbcddddeeee
(5 rows)


You need to know the greatest upper dimension of the array, in this case
3, for the generate_series - function.


Andreas
-- 
Andreas Kretschmer
Kontakt:  Heynitz: 035242/47150,   D1: 0160/7141639 (mehr: -> Header)
GnuPG-ID:   0x3FFF606C, privat 0x7F4584DA   http://wwwkeys.de.pgp.net

am  Thu, dem 22.02.2007, um 14:25:36 +0100 mailte A. Kretschmer folgendes:
> test=*# select * from a;
>       c
> -------------
>  {aaa,bb,c}
>  {dddd,eeee}
>  {aaa,eeee}
> (3 rows)
> 
> 
> test=*# select distinct c[s] from a,  generate_series(1,3)s where c[s] is not null;
>   c
> ------
>  aaa
>  bb
>  c
>  dddd
>  eeee
> (5 rows)
> 
> 
> You need to know the greatest upper dimension of the array, in this case
> 3, for the generate_series - function.

select distinct c[s] from a,  generate_series(1,(select max(array_upper(c,1)) from a))s where c[s] is not null;

;-)


Andreas
-- 
Andreas Kretschmer
Kontakt:  Heynitz: 035242/47150,   D1: 0160/7141639 (mehr: -> Header)
GnuPG-ID:   0x3FFF606C, privat 0x7F4584DA   http://wwwkeys.de.pgp.net