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#1 (**permalink**) 04-10-2008, 10:59 AM

Please, help me!
My code:
"IF char_length(substring(str from '^[a-zA-Z]*://'))=0 THEN
str:= 'http://'||str;
END IF;"

If str= http://www.msn.com then nothing happen
(all is OK), but if str= just www.msn.com then nothing happen too!

Why?

Then I experimen with that:
I change '=' to '<>'
results:
str=http://www.msn.com -> http://http://www.msn.com
str=www.msn.com -> http://www.msn.com

Thank you.

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TIP 9: In versions below 8.0, the planner will ignore your desire to
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#2 (**permalink**) 04-10-2008, 10:59 AM

On Thu, 26 Jul 2007, [UTF-8] Ð¢Ñ^CÑ^GÐºÐ¾Ð² Ð^\Ð¸Ñ^EÐ°Ð¸Ð» wrote:

> Please, help me!
> My code:
> "IF char_length(substring(str from '^[a-zA-Z]*://'))=0 THEN
> str:= 'http://'||str;
> END IF;"
>
> If str= http://www.msn.com then nothing happen
> (all is OK), but if str= just www.msn.com then nothing happen too!
>
> Why?

According to:
http://www.postgresql.org/docs/8.2/i...-matching.html
a non-match returns NULL, whose char_length is also NULL.

Using one of the regexp operators ~ or ~* would probably be easier, but if
you really wanted to do this with substring, you should be checking for no
match, not a 0 length match.

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TIP 6: explain analyze is your friend

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