MySQL making whitespace matter -

-

apparently rare issue, imo extremely annoying , wrong: trailing whitespace in mysql aren't used in comparison:

mysql> select "a" = "a "; +------------+ | "a" = "a " | +------------+ |          1 | +------------+ 1 row in set (0.00 sec)

this problematic in following scenario:

mysql> select count(*) eq name != trim(name); +------------+ | count(*)   | +------------+ |          0 | +------------+ 1 row in set (0.00 sec)  mysql> update eq set name=trim(name); query ok, 866 row affected (0.01 sec) rows matched: 650907  changed: 866  warnings: 0

is there way configure mysql treat whitespace properly?

according the manual, 1 quick fix use like:

per sql standard, performs matching on per-character basis, can produce results different = comparison operator:

...

in particular, trailing spaces significant, not true char or varchar comparisons performed = operator ...

as long don't use wildcards, should identical =. stack overflow question seems support assumption: equals(=) vs. like

the manual doesn't state whether strcmp() stricter = in terms of whitespace, , can't try out right - might worth taking at, too, makes clearer why = not used.

binary comparison suggested tombom option, have other side-effects (like stricter comparison of umlauts, eg. a , Ä different) may or may not want. more info on effects of using binary comparison in this question.


Comments

Post a Comment

Popular posts from this blog

c# - SVN Error : "svnadmin: E205000: Too many arguments" -

-
i trying reposotries using c# code process svncommand = null; var psi = new processstartinfo("svnadmin"); psi.redirectstandardoutput = true; psi.redirectstandarderror = true; psi.useshellexecute = false; psi.arguments= @"dump c:\repositories\myrepo > c:\temp\myrepodumpfile.dump"; using (svncommand = process.start(psi)) { var myoutput = svncommand.standardoutput; var myerror = svncommand.standarderror; debug.write("output :" + environment.newline + environment.newline + myoutput.readtoend() + environment.newline + "error :" + environment.newline + environment.newline + myerror.readtoend()); svncommand.close(); } when use dump command commandline svnadmin dump c:\repositories\myrepo > c:\temp\myrepodumpfile.dump it works fine when try ...
Read more

c++ - Using OpenSSL in a multi-threaded application -

-
i have been writing soap client application in c++ on ubuntu using openssl https transport , pthreads threading. have number of threads - 1 central data acquisition thread periodically gets worker threads make soap requests via shared mutex protected queues. reading documentation openssl found is openssl thread-safe? in openssl faq describes mechanisms required ensure thread safety when using openssl. implemented , works fine. the reason question conceptual difficulty really. thinking implementing same functionality application has already, instead of using threads, create 2 seperate applications : 1 worker thread (of multiple copies running) , main data acquisition thread. use tcp sockets communicate between 2 rather mutex protected queues. may bad idea not important - confusing me would have implement same functions required ensure openssl thread safety in second approach or not? my guess not have , treated independent (indeed surely must many applications use openssl) re...
Read more

All overlapping substrings matching a java regex -

-
is there api method returns (possibly overlapping) substrings match regular expression? for example, have text string: string t = 04/31 412-555-1235; , , have pattern: pattern p = new pattern("\\d\\d+"); matches strings of 2 or more characters. the matches are: 04, 31, 412, 555, 1235. how overlapping matches? i want code return: 04, 31, 41, 412, 12, 55, 555, 55, 12, 123, 1235, 23, 235, 35. theoretically should possible -- there obvious o(n^2) algorithm enumerates , checks substrings against pattern. edit rather enumerating substrings, safer use region(int start, int end) method in matcher . checking pattern against separate, extracted substring might change result of match (e.g. if there non-capturing group or word boundary check @ start/end of pattern). edit 2 actually, it's unclear whether region() expect zero-width matches. specification vague, , experiments yield disappointing results. for example: string line = "xx90xx"; strin...
Read more