oracle create index if not exists
DECLARE
already_exists EXCEPTION;
columns_indexed EXCEPTION;
PRAGMA EXCEPTION_INIT ( already_exists, -955 );
PRAGMA EXCEPTION_INIT (columns_indexed, -1408);
BEGIN
EXECUTE IMMEDIATE 'CREATE INDEX ord_customer_ix ON orders (customer_id)';
dbms_output.put_line('created');
EXCEPTION
WHEN already_exists OR columns_indexed THEN
dbms_output.put_line('skipped');
END;