You need to create the NSMutableArray
once and make all additions to it.
NSMutableArray *list = [[NSMutableArray alloc] init];
while (sqlite3_step(searchStatement) == SQLITE_ROW)
{
NSString *nickname = [NSString stringWithUTF8String:(char *)sqlite3_column_text(searchStatement, 0)];
NSString *time = [NSString stringWithUTF8String:(char *)sqlite3_column_text(searchStatement, 1)];
NSString *text = [NSString stringWithUTF8String:(char *)sqlite3_column_text(searchStatement, 2)];
[list addObject:nickname];
[list addObject:time];
[list addObject:text];
...
}
[list writeToFile:filePATH atomically:YES];