Re: [sqlite] a question on the callback function's return values of sqlite3_exec()
Thank you very much! this is my first time to use sqlite3. using prepared statements is a little difficult. Could I avert to another way(more simple way) to achieve the same thing? Or where could I get some example codes on the method of using prepared statements? Igor Tandetnik wrote: > > "liubin liu" <7101...@sina.com> wrote in message > news:22176984.p...@talk.nabble.com >> the question is on the callback function's return values of >> sqlite3_exec() >> >> when using sqlite3_exec() to do "select * from ...", how to get all >> the return values by using the callback function? >> >> it could print the result, but couldn't return the values. If do like >> so, just one value could be get. >> how to get all the values? > > Memory allocated for value[] strings is valid only inside the callback. > It is deallocated or reused as soon as the callback returns. So, you > can't just store a pointer you receive - it'll soon become invalid. You > need to allocate your own memory and make a copy of string contents. > > Also, consider using prepared statements instead of sqlite3_exec - see > sqlite3_prepare, sqlite3_step, sqlite3_finalize, sqlite3_column_*. For > one thing, values of numeric fields could be retrieved directly as > integers, rather than converted to strings and then converted back. > > Igor Tandetnik > > > > ___ > sqlite-users mailing list > sqlite-users@sqlite.org > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users > > -- View this message in context: http://www.nabble.com/a-question-on-the-callback-function%27s-return-values-of-sqlite3_exec%28%29-tp22176984p22194312.html Sent from the SQLite mailing list archive at Nabble.com. ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
Re: [sqlite] a question on the callback function's return values of sqlite3_exec()
"liubin liu" <7101...@sina.com> wrote in message news:22176984.p...@talk.nabble.com > the question is on the callback function's return values of > sqlite3_exec() > > when using sqlite3_exec() to do "select * from ...", how to get all > the return values by using the callback function? > > it could print the result, but couldn't return the values. If do like > so, just one value could be get. > how to get all the values? Memory allocated for value[] strings is valid only inside the callback. It is deallocated or reused as soon as the callback returns. So, you can't just store a pointer you receive - it'll soon become invalid. You need to allocate your own memory and make a copy of string contents. Also, consider using prepared statements instead of sqlite3_exec - see sqlite3_prepare, sqlite3_step, sqlite3_finalize, sqlite3_column_*. For one thing, values of numeric fields could be retrieved directly as integers, rather than converted to strings and then converted back. Igor Tandetnik ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
[sqlite] a question on the callback function's return values of sqlite3_exec()
the question is on the callback function's return values of sqlite3_exec()
when using sqlite3_exec() to do "select * from ...", how to get all the
return values by using the callback function?
struct olt_info
{
int olt_index;
int olt_logo;
char* olt_line;
// int nmber;
};
int my_callback(void *olt_temp, int argc, char *value[], char *name[])
{
struct olt_info *pdata = NULL;
pdata = (struct olt_info *)olt_temp;
int jj;
for (int i = 0; i < argc; i++)
jj = printf("%s == %s\n", name[i], value[i]);
pdata->olt_index = (int)atoi(value[0]);
pdata->olt_logo = (int)atoi(value[1]);
pdata->olt_line = value[2];
return 0;
}
it could print the result, but couldn't return the values. If do like so,
just one value could be get.
how to get all the values?
--
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http://www.nabble.com/a-question-on-the-callback-function%27s-return-values-of-sqlite3_exec%28%29-tp22176984p22176984.html
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