Check if a value exists in database table

Replace this:

$result = $wpdb->get_row("SELECT * FROM wp44_predefined_address WHERE 'UPPER(Address1)' LIKE 'UPPER(%s)'", $myinput);

with this: (just choose the appropriate $like based on your requirements)

// Properly generate the LIKE query.
$like="%" . $wpdb->esc_like( $myinput ) . '%'; // e.g. '%input%'
//$like="%" . $wpdb->esc_like( $myinput ); // e.g. '%input'
//$like = $wpdb->esc_like( $myinput ) . '%'; // e.g. 'input%'

$result = $wpdb->get_row("SELECT * FROM wp44_predefined_address WHERE Address1 LIKE %s", $like);