Fatal error: Uncaught mysqli_sql_exception: Duplicate column name 'marker_ids' in C:\Apache24\htdocs\update\update_3.php:31 Stack trace: #0 C:\Apache24\htdocs\update\update_3.php(31): mysqli_query(Object(mysqli), 'alter table gs_...') #1 {main} thrown in C:\Apache24\htdocs\update\update_3.php on line 31