Table not Alter

I want to add Unique query in combination of Two column.I am using this but this is not able make Unique. Please help Any help would be apperciated.

updateSQL = [NSString stringWithFormat:@"CREATE TABLE IF NOT EXISTS NewsData (id INTEGER PRIMARY KEY AUTOINCREMENT,NewsId TEXT  ,NewsValue TEXT,Title TEXT,Region INTEGER)"];
    update_stmt = [updateSQL UTF8String];
    sqlite3_prepare_v2(database, update_stmt, -1, &addStatement, NULL);
    sqlite3_step(addStatement);
    sqlite3_reset(addStatement);


    updateSQL = [NSString stringWithFormat:@"ALTER TABLE NewsData ADD UNIQUE (NewsId, Region)"];
    update_stmt = [updateSQL UTF8String];
    sqlite3_prepare_v2(database, update_stmt, -1, &addStatement, NULL);
    sqlite3_step(addStatement);
    sqlite3_reset(addStatement);