I have read the wrong line in my inbox while typing my reply. Hopefully you forgive me ;)
Am 25.11.2012 17:11, schrieb Imanuel: > Hi Keith > >> UPDATE user SET a=1,b=2,c=3 WHERE a||b||c!=1||2||3; > > It seems to me that this is not reliable. > Think the the following text values: > a='12' > b='34' > c='56' > > If you want to update these values to: > a='1' > b='2345' > c='6' > > Then your statement would not update because '123456' = '123456'. > > Greetings > > > > Am 25.11.2012 17:04, schrieb Simon Slavin: >> >> On 25 Nov 2012, at 10:46am, Keith Chew <keith.c...@gmail.com> wrote: >> >>> I found that when an update SQL is issued against a table, the WAL file >>> gets updated with the new record, even though the record is exactly the >>> same as the current record. >>> >>> [snip] >>> >>> Is there a specific reason for this? Is there a way to improve this by not >>> inserting the record into the WAL file if the final record is not changed? >> >> I think it would take SQLite a lot of time to read every row to see whether >> the UPDATE command will change it before generating the new entry. Most >> people's code wouldn't issue such a command under those circumstances. >> Richard's suggesting of >> >>> UPDATE user SET user_name='Keith' WHERE user_name!='Keith'; >> >> is what you're asking for. With that many columns (which is unusual, >> generally you should be able to keep an entire schema in your head) you can >> either check them one by one, or concatenate them all together and check to >> see that the long concatenation hasn't changed: >> >> UPDATE user SET a=1,b=2,c=3 WHERE a||b||c!=1||2||3; >> >> I seem to remember that this is a database where you have every column, of >> 40 to 50 columns, indexed. This is also unusual, and not something that >> SQLite is optimized for, and you're going to get unusual results from it. >> >> Simon. >> _______________________________________________ >> sqlite-users mailing list >> sqlite-users@sqlite.org >> http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users >> > _______________________________________________ > sqlite-users mailing list > sqlite-users@sqlite.org > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users > _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
