Reverse a text in PostgreSQL

Monday, July 24. 2006

Reverse a text in PostgreSQL

Andreas 'ads' Scherbaum

I'm always searching for a reverse function, so here is the link:

http://www.varlena.com/GeneralBits/53.php

code snippet is available in plperl and plpgsql.

Posted by Andreas 'ads' Scherbaum in Code Snippets at 21:36 | Comments (0) | Trackbacks (0)

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Using recursion, one can also achieve it with a plain sql function: create function reverse(text) returns text as $$ select case when length($1)>0 then substring($1, length($1), 1) || reverse(substring($1, 1, length($1)-1)) else '' end $$ language sql immutable strict;

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#1 dys on 2006-07-28 19:20 (Reply)

a code from Varlena is not good - there is a few issues - first issue is using a WHILE statement. FOR statement is better - is faster. And you can use a simple and relative fast SQL function create or replace function rvrs(text) returns text as $$ select string_agg(substring($1 from i for 1),'') from generate_series(length($1),1,-1) g(i) $$ language sql;

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#2 Pavel Stehule (Homepage) on 2011-07-27 18:36 (Reply)

Here is one more function to reverse text that uses FOR statement if anybody interested. create or replace function rev(varchar) returns varchar as $$ declare _temp varchar; _count int; begin _temp := ''; for _count in reverse length($1)..1 loop _temp := _temp || substring($1 from _count for 1); end loop; return _temp; end; $$ language plpgsql immutable;

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#3 Alexandr (Homepage) on 2011-09-24 17:42 (Reply)

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