2018. 05. 07. 12:26 keltezéssel, Dimitry Sibiryakov s...@ibphoenix.com
[firebird-support] írta:
> 07.05.2018 12:19, Gabor Boros mlngl...@bgss.hu [firebird-support] wrote:
>> A simple example: SELECT ''='' SIMILAR TO '[A-Z]{2}[0-9A-Z]{2,13}' FROM
>> RDB$DATABASE
>>
>> Why is the result true?
>
> Your expression is actually calculated as "CAST(''='' as CHAR(5)) SIMILAR
> TO
> '[A-Z]{2}[0-9A-Z]{2,13}'".
> (''='') is true and string representation of true is 'TRUE ' that matches
> your patters.
Result of
SELECT '*' || CAST(''='' AS CHAR(5)) || '*',
CHARACTER_LENGTH(CAST(''='' AS CHAR(5))) FROM RDB$DATABASE
is
CONCATENATION CHAR_LENGTH
============= ============
*TRUE * 5
So I see what you say. But result of
SELECT CAST(''='' AS CHAR(5)) SIMILAR TO '[A-Z]{2}[0-9A-Z]{2,13}' FROM
RDB$DATABASE;
is
=======
<false>
So put the two case into one query
SELECT ''='' SIMILAR TO '[A-Z]{2}[0-9A-Z]{2,13}', CAST(''='' AS
CHAR(5)) SIMILAR TO '[A-Z]{2}[0-9A-Z]{2,13}' FROM RDB$DATABASE;
and the result is
======= =======
<true> <false>
And result of
SELECT 'TRUE ' SIMILAR TO '[A-Z]{2}[0-9A-Z]{2,13}' FROM RDB$DATABASE
is
=======
<false>
Gabor
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