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 ------------------------------------ ------------------------------------ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Visit http://www.firebirdsql.org and click the Documentation item on the main (top) menu. Try FAQ and other links from the left-side menu there. Also search the knowledgebases at http://www.ibphoenix.com/resources/documents/ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ ------------------------------------ Yahoo Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/firebird-support/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/firebird-support/join (Yahoo! ID required) <*> To change settings via email: firebird-support-dig...@yahoogroups.com firebird-support-fullfeatu...@yahoogroups.com <*> To unsubscribe from this group, send an email to: firebird-support-unsubscr...@yahoogroups.com <*> Your use of Yahoo Groups is subject to: https://info.yahoo.com/legal/us/yahoo/utos/terms/