iOS: filter SQLite query / check entry against former entries

Okay, so I'm doing a search in a SQLite database for all entries in the row called Artists... But I don't want the same artist to appear twice...

-(NSArray *)findAllArtists
{
    NSMutableArray *returnArray = [[[NSMutableArray alloc] init] autorelease];

    NSString *query = @"SELECT * FROM Painting";

    sqlite3_stmt *statement;

    if (sqlite3_prepare_v2(database, [query UTF8String], -1, &statement, nil) 
    == SQLITE_OK) 
    {        
        while (sqlite3_step(statement) == SQLITE_ROW) 
        {
            char *uniqueIdChars = (char *) sqlite3_column_text(statement, 0);
            char *artistChars = (char *) sqlite3_column_text(statement, 1);
            NSString *uniqueId = [[NSString alloc] initWithUTF8String:uniqueIdChars];
            NSString *artist = [[NSString alloc] initWithUTF8String:artistChars];

            PaintingInfo *info = [[P开发者_开发技巧aintingInfo alloc] initWithUniqueId:uniqueId artist:artist];
            [returnArray addObject:info];

            [uniqueId release];
            [artist release];
        }

        sqlite3_finalize(statement);
    }

    sqlite3_close(database);
    return returnArray;    
}

So, what I'm thinking is that one way could be to use a loop inside before adding the result to the returnArray, where I check if it matches a previous result... It sounds fairly simply, but for some reason, I haven't gotten the loops I've tried to work (think I might have been working too long without sleep, so I'm starring blindly at my errors)... Then again, I'm fairly new to SQLite, so it might be a poor way of going about it...

Any suggestions?

Why not let the sql engine do the work? Do a select distinct

http://www.sqlite.org/lang_select.html

example:

SELECT DISTINCT artist FROM Painting

If for some reason you need to do it in code in the loop as your processing, you can look at NSSet which is a hash set. You would add each artist to the set as you process it and check if in the set before processing.

http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSSet_Class/Reference/Reference.html

For example, this:

NSArray *artists = [NSArray arrayWithObjects:@"bob", @"jane", @"jane", nil];

NSMutableSet *distinctArtists = [[NSMutableSet alloc] init];
NSMutableArray *list = [[NSMutableArray alloc] init];
for (NSString* artist in artists)
{
    if (![distinctArtists containsObject:artist])
    {
        [distinctArtists addObject:artist];
        [list addObject:artist];
    }
}

// print
for (NSString *artist in list)
{
    NSLog(@"artist: %@", artist);
}

outputs:

2011-10-06 22:51:16.457 Craplet[1982:707] artist: bob
2011-10-06 22:51:16.459 Craplet[1982:707] artist: jane

SELECT * FROM Painting GROUP BY Artist had the same effect