The code is

DECLARE
message VARCHAR(30);
BEGIN
message := 'Welcome to the Oracle World';
EXECUTE IMMEDIATE 'alter table emp add Desc_ription varchar(30)';

UPDATE emp
SET desc_ription = message;

COMMIT;
END;

I get the following error.

ORA-06550: line 6, column 26:
PLS-00417: unable to resolve "DESC_RIPTION" as a column
ORA-06550: line 6, column 1:
PL/SQL: SQL Statement ignored