iOS 6: Trying to select from 2 databases from different paths - ios

Question

I have two databases.
ch_coins.db is read-only data for tableview in [NSBundle mainBundle].
User_data.sqlite in Documents
I try to combine select from both databases and fill data to object. My method is like that:
-(NSMutableArray*)returnSubCountries
{
NSString *path = [[[NSBundle mainBundle] resourcePath]
stringByAppendingPathComponent:databaseName];
NSArray *paths = NSSearchPathForDirectoriesInDomains (NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDir = [paths objectAtIndex:0];
NSString *userDB = [documentsDir stringByAppendingPathComponent:user_data];
NSMutableArray *subCountiresArr=[[NSMutableArray alloc]init];
if (sqlite3_open([path UTF8String], &database) == SQLITE_OK)
{
/*const char *sqlSubCountries="SELECT subCountryID,subCountryName,subCountryComment,image,priority,hasRegions,navigationKey\
FROM subCountries\
ORDER BY priority ASC";*/
const char *sqlSubCountries="SELECT subCountryID,subCountryName,subCountryComment,image,priority,hasRegions,navigationKey,usdb.quantity\
attach database 'userDB' as usdb\
INNER JOIN usdb on subCountries.subCountryID=usdb.refID\
FROM subCountries\
ORDER BY priority ASC";
sqlite3_stmt *statement;
int sqlResult = sqlite3_prepare_v2(database, sqlSubCountries, -1, &statement, NULL);
if ( sqlResult== SQLITE_OK)
{
while (sqlite3_step(statement) == SQLITE_ROW)
{
SubCountry *sbCountryObj=[[SubCountry alloc]init];
sbCountryObj.subCountryID=sqlite3_column_int(statement, 0);
char *subCountryName=(char *)sqlite3_column_text(statement, 1);
char *subCountryComment=(char *)sqlite3_column_text(statement, 2);
char *image=(char *)sqlite3_column_text(statement, 3);
sbCountryObj.priority=sqlite3_column_int(statement, 4);
sbCountryObj.hasRegions=(sqlite3_column_int(statement, 5)==1);
sbCountryObj.navigationKey=sqlite3_column_int(statement, 6);
sbCountryObj.quantity=sqlite3_column_int(statement, 7);
sbCountryObj.subCountryName=(subCountryName)?[NSString stringWithUTF8String:subCountryName]: #"";
sbCountryObj.subCountryComment=(subCountryComment)?[NSString stringWithUTF8String:subCountryComment]: #"";
sbCountryObj.image=(image)?[NSString stringWithUTF8String:image]: #"";
[subCountiresArr addObject:sbCountryObj];
}
sqlite3_finalize(statement);
sqlite3_close(database);
}
}
else
{
//[self dbConnectionError];
}
return subCountiresArr;
}
I must be doing something wrong. any help is much appreciated. Thanx.
EDIT:
-(NSMutableArray*)returnSubCountries
{
NSString *path = [[[NSBundle mainBundle] resourcePath]
stringByAppendingPathComponent:databaseName];
NSArray *paths = NSSearchPathForDirectoriesInDomains (NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDir = [paths objectAtIndex:0];
NSString *userDB = [documentsDir stringByAppendingPathComponent:user_data];
NSMutableArray *subCountiresArr=[[NSMutableArray alloc]init];
if (sqlite3_open([path UTF8String], &database) == SQLITE_OK)
{
/*const char *sqlSubCountries="SELECT subCountryID,subCountryName,subCountryComment,image,priority,hasRegions,navigationKey\
FROM subCountries\
ORDER BY priority ASC";*/
NSString *userDBName = [NSString stringWithFormat:#"attach database '%#' as usdb", userDB];
const char *sqlAttachedDatabase = [userDBName UTF8String];
const char *sqlSubCountries="SELECT subCountryID,subCountryName,subCountryComment,image,priority,hasRegions,navigationKey,usdb.quantity\
sqlAttachedDatabase userDB as usdb\
INNER JOIN usdb on subCountries.subCountryID=usdb.refID\
FROM subCountries\
ORDER BY priority ASC";
sqlite3_stmt *statement;
int sqlResult = sqlite3_prepare_v2(database, sqlSubCountries, -1, &statement, NULL);
if ( sqlResult== SQLITE_OK)
{
while (sqlite3_step(statement) == SQLITE_ROW)
{
SubCountry *sbCountryObj=[[SubCountry alloc]init];
sbCountryObj.subCountryID=sqlite3_column_int(statement, 0);
char *subCountryName=(char *)sqlite3_column_text(statement, 1);
char *subCountryComment=(char *)sqlite3_column_text(statement, 2);
char *image=(char *)sqlite3_column_text(statement, 3);
sbCountryObj.priority=sqlite3_column_int(statement, 4);
sbCountryObj.hasRegions=(sqlite3_column_int(statement, 5)==1);
sbCountryObj.navigationKey=sqlite3_column_int(statement, 6);
sbCountryObj.quantity=sqlite3_column_int(statement, 7);
sbCountryObj.subCountryName=(subCountryName)?[NSString stringWithUTF8String:subCountryName]: #"";
sbCountryObj.subCountryComment=(subCountryComment)?[NSString stringWithUTF8String:subCountryComment]: #"";
sbCountryObj.image=(image)?[NSString stringWithUTF8String:image]: #"";
[subCountiresArr addObject:sbCountryObj];
}
sqlite3_finalize(statement);
sqlite3_close(database);
}
else
{
NSLog(#"%s: prepare failed: %s", __FUNCTION__, sqlite3_errmsg(database));
}
}
else
{
//[self dbConnectionError];
}
return subCountiresArr;
}

Answer 1

You're specifying the database path as userDB in your SQL, but that's not the name of the database file. That is, the name of the variable that has the full path name in it, but you presumably actually have to build your SQL with that filename. For example:
NSString *sql = [NSString stringWithFormat:#"attach database '%#' as usdb", userDB];
const char *sqlAttachedDatabase = [sql UTF8String];
Execute that. Then, as a separate statement, you can execute your SELECT SQL that uses the usdb alias. And when you're done, detach the database.
Also, I notice that you're checking to see if the result is SQLITE_OK (which is good). But you're not showing any diagnostic information if it's not. For example, your SQL is wrong, but you're not showing a meaningful error message. Thus, if your sqlite3_prepare_v2 fails to return SQLITE_OK, you should:
NSLog(#"%s: prepare failed: %s", __FUNCTION__, sqlite3_errmsg(database));
If you do this when you have an error, you'll be able to figure out what's wrong. Without that, you're flying blind.
A working example, where my "author" database is in the bundle, and my "book" database is in Documents:
int rc;
NSString *docsPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
NSString *bookFilename = [docsPath stringByAppendingPathComponent:#"book.sqlite"];
NSString *authorFilename = [[NSBundle mainBundle] pathForResource:#"author" ofType:#"sqlite"];
sqlite3 *database;
if ((rc = sqlite3_open([authorFilename UTF8String], &database)) != SQLITE_OK)
{
NSLog(#"%s: open failed: %s (%d)", __FUNCTION__, sqlite3_errmsg(database), rc);
return;
}
NSString *sql = [NSString stringWithFormat:#"attach database '%#' as userdb;", bookFilename];
if ((rc = sqlite3_exec(database, [sql UTF8String], NULL, NULL, NULL)) != SQLITE_OK)
NSLog(#"%s: attach failed: %s (%d)", __FUNCTION__, sqlite3_errmsg(database), rc);
sqlite3_stmt *statement;
sql = #"select book.*, author.* from userdb.book inner join author on author_id = book_author_id;";
if ((rc = sqlite3_prepare_v2(database, [sql UTF8String], -1, &statement, NULL)) != SQLITE_OK)
NSLog(#"%s: prepare failed: %s (%d)", __FUNCTION__, sqlite3_errmsg(database), rc);
while ((rc = sqlite3_step(statement)) == SQLITE_ROW)
{
// do whatever you want row by row
NSLog(#"Row");
}
if (rc != SQLITE_DONE)
NSLog(#"%s: step failed: %s (%d)", __FUNCTION__, sqlite3_errmsg(database), rc);
sqlite3_finalize(statement);
sql = #"detach database userdb;";
if ((rc = sqlite3_exec(database, [sql UTF8String], NULL, NULL, NULL)) != SQLITE_OK)
NSLog(#"%s: detach failed: %s (%d)", __FUNCTION__, sqlite3_errmsg(database), rc);
sqlite3_close(database);

Answer 2

You should do the following:
Run SQL "attach database 'full db path' as usdb", where "full db path" is full path to database file
Prepare and execute SELECT statement (remove "attach database ..." from it)
Detach database when it's not needed "detach database 'full db path'"