2009/11/11 TTTTT <erlichk...@gmail.com>:
>
> i`ve done it, and i think i understand it :)
>
> thank you..
>
>
> few more question to be sure that i`m not missing something important..
>
> if i use prepared statements only (dont use exec function in program at all)
> i dont need callback function, do i?
No
> somehow after i replaced exec (i.e. select_statement function) and i dont
> need select_statement function, neither callback function, evetything seems
> much more simple (which is why i`m bit suspicious if i`ve done everything
> correct)..
>
> are there any cases when it is better to use exec ?
<shrug>
perhaps simpler/quicker to code for sql that returns no data (INSERT etc)
</shrug>
>
>
> does using prepared statement slow down my program since prepare function is
> used every time when i want to execute some command ?
No - sqlite3_exec() is a wrapper around sqlite3_prepare()/sqlite3_step()
> here is how my
> function looks like now:
>
> bool create2 (char * command)
> {
>
> sqlite3_stmt * statement2;
>
> if ( sqlite3_prepare (db, command, -1, &statement2, 0) != SQLITE_OK )
> {
> int err = sqlite3_prepare (db, command, -1, &statement2, 0);
no need to call prepare a second time - assign to err in your if
statement, or use sqlite3_errcode()
> const char * pErr = sqlite3_errmsg (db);
> printf ("\nError %d occured! \n %s", err, pErr );
> return false;
> }
>
> int iCol = sqlite3_column_count (statement2);
>
> int smth, i;
> //int rows=1;
> smth=sqlite3_step(statement2);
>
> while (smth == SQLITE_ROW)
> {
> printf ("\n");
> //printf ("\n Row %d:\t", rows); // doesnt give right number of
> column
> for other select statements except select all
> for (i=0; i<iCol; i++)
> {
> const char *txt = (const char*)sqlite3_column_text(statement2,
> i); // save
> it into dynamical multidimensional array
> printf (" %s = %s \t", sqlite3_column_name (statement2,i), txt
> );
> }
> printf ("\n");
> //rows++;
> smth=sqlite3_step (statement2);
>
> }
>
> sqlite3_reset (statement2);
Use sqlite3_reset if you are going to bind new values to your prepared
statement and restep. If you are finalizing there is no need to reset.
> sqlite3_finalize (statement2);
>
> return true;
> }
>
>
> main:
>
>
> create2 ("CREATE TABLE two (ID INTEGER PRIMARY KEY ASC, a,b,c)");
> create2 ("INSERT INTO two (a,b) VALUES (3, 4)");
> create2 ("INSERT INTO two (a,b,c) VALUES (2, 8, 9)");
> create2 ("INSERT INTO two (a,c) VALUES (4, 1)");
> create2 ("INSERT INTO two (a,b,c) VALUES (1, 4, 9)");
> create2 ("INSERT INTO two (a,b,c) VALUES (1, 2, 8)");
> create2 ("SELECT * FROM two");
> create2 ("SELECT * FROM two WHERE b=4");
>
>
> if you have some advices or suggestions please let me know..
>
Regards,
Simon
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