> As the last three statements are exactly the same (in meaning). > Can someone explain what's happening?
I think you've got trapped by double value storage imprecision. Comparing double values for exact equality is pretty dangerous - two numbers can differ in one last bit, be not equal and be displayed identically when printed in decimal form. Pavel On Tue, May 8, 2012 at 9:34 AM, elmo <[email protected]> wrote: > I have code that looks like that: > > --- begin main.cpp --- > > #include <unistd.h> > #include <stdio.h> > #include <sqlite3.h> > #include <string.h> > > void print( sqlite3_stmt * pStmt ) > { > const char* col1name = sqlite3_column_name( pStmt, 0 ); > printf("res: "); > > while ( sqlite3_step( pStmt ) == SQLITE_ROW ){ > printf("%lf ", sqlite3_column_double( pStmt, 0 )); > } > printf("\n"); > > sqlite3_finalize(pStmt); > } > > int main( int argc, char ** argv ) > { > const char filename[] = "test.db3"; > char * err = 0; > > unlink( filename ); > > sqlite3 *db; > sqlite3_open( filename, &db ); > > sqlite3_exec(db, "create table test (a decimal(12,4))", 0, 0, &err); > sqlite3_exec(db, "insert into test values (123.456)", 0, 0, &err); > > sqlite3_stmt * q; > char buf[2048]; > > strcpy( buf, "select * from test"); > sqlite3_prepare(db, buf, sizeof(buf), &q, NULL); > print( q ); > > strcpy( buf, "select * from test where a = ?"); > sqlite3_prepare(db, buf, sizeof(buf), &q, NULL); > sqlite3_bind_text( q, 1, "123.456", 7, SQLITE_STATIC ); > print( q ); > > strcpy( buf, "select sum(a) from test group by a"); > sqlite3_prepare(db, buf, sizeof(buf), &q, NULL); > print( q ); > > strcpy( buf, "select sum(a) from test group by a having sum(a) = 123.456"); > sqlite3_prepare(db, buf, sizeof(buf), &q, NULL); > print( q ); > > strcpy( buf, "select sum(a) from test group by a having sum(a) = ?"); > sqlite3_prepare(db, buf, sizeof(buf), &q, NULL); > sqlite3_bind_text( q, 1, "123.456", 7, SQLITE_STATIC ); > print( q ); > > strcpy( buf, "select sum(a) from test group by a having sum(a) = 0+?"); > sqlite3_prepare(db, buf, sizeof(buf), &q, NULL); > sqlite3_bind_text( q, 1, "123.456", 7, SQLITE_STATIC ); > print( q ); > > return 0; > } > > --- end main.cpp --- > > The output is: > > res: 123.456000 > res: 123.456000 > res: 123.456000 > res: 123.456000 > res: > res: 123.456000 > > Whereas I would expect it to be: > > res: 123.456000 > res: 123.456000 > res: 123.456000 > res: 123.456000 > res: 123.456000 > res: 123.456000 > > As the last three statements are exactly the same (in meaning). > Can someone explain what's happening? > _______________________________________________ > sqlite-users mailing list > [email protected] > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users _______________________________________________ sqlite-users mailing list [email protected] http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
