Mysql add mult-column index with repeated rows -

-

having next table:

id -> incremental field_1 -> foreignkey field_2 -> foreignkey

i want add next index 

alter table my_table add unique index(field_1, field_2);

how ever have (due bad application validation) have lot of repeated rows (by repeated mean same field_1 , same field_2, having id difference)

the table has 60,000 rows so... removing field field hard.

how can apply index , remove every duplicated row?

create table mytable2 mytable;  insert mytable2  select max(id), field_1, field_2  mytable  group field_1, field_2;  rename table mytable mytable_old, mytable2 mytable;  alter table my_table add unique index(field_1, field_2)

Comments

Post a Comment

Popular posts from this blog

c++ - Compiling static TagLib 1.6.3 libraries for Windows -

-
i having super hard time compiling , using taglib 1.6.3 in qt project. i've tried can think of. taglib claims supported through cmake i'm not having luck. furthermore, i'm confused kinds of files need qt libs! i've built *.a files, *.lib, , *.dll. understand far... believe since i'm working in windows *.lib want. no matter do, end "undefined references" taglib functions try use when try compile qt project. have tried mingw32, msys, visual studio 2008, , cross-compiling windows on linux. turning nothing. what makes less sense me if compile same taglib source qt on mac (g++ think?) works fine! somewhere in windows compilation procedures have going wrong. have been smacking face on desk 30 (on , off) hours trying figure out. since qt uses mingw must compile taglib same compiler? if compile *.lib's visual studio not compatible? are *.a libraries usable in windows? (assuming mingw) i'm still trying handle on c++ stuff, after reading coun...
Read more

PostgreSQL 9.x - pg_read_binary_file & inserting files into bytea -

-
i have been looking everywhere (google, stackoverflow, etc.) documentation on how use postgresql pg_read_binary_file() function. the meaningful thing can find this page in official documentation. every time try use function error. for example: select pg_read_binary_file('/some/path/and/file.gif'); error: absolute path not allowed or select pg_read_binary_file('file.gif'); error: not stat file "file.gif": no such file or directory do need have file in specific directory postgres have access it? if directory? if matters, reason looking @ function because trying insert file database without doing crazy things . as stated @a_horse_with_no_name , @guedes solution ensure file being uploaded on server in pgdata directory. the postgres documentation state file location requirement. additionally, made symlink directory pgdata directory not disturb of postgres data structure. seems working , don't have of above...
Read more

asp.net - call stack missing info on mono with apache and mod_mono -

-
how enable debugging/stacktrace filenames , numbers apache2/mod_mono? instead of filenames , numbers this at system.web.staticfilehandler.processrequest (system.web.httpcontext context) [0x00000] in <filename unknown>:0 i tried using monodebug true in apache , recompile mod_mono --enable-debug , have <compilation debug="true"> inside of configuration>system.web>httpruntime in web.config. i using debian lenny , tried installing mono-debugger, restart apache , still no luck. used configuration tool no luck. many supported on suse? http://go-mono.com/config-mod-mono/ i had same problem. there quite few solutions. first of all, must install mono-core-debuginfo package, or might not work. second, must run mono in debug mode *solution 1: add virtual host section/httpd.conf monosetenv monodebug true *solution 2: start xsp/mod-mono-server debug $ mono_options=--debug xsp2
Read more