✅ Initial Table Description
DESC EMPLOYEE;
Result:
| Name | Null? | Type |
| ---------- | ---------- | ------------ |
| USERNAME | NOT NULL | VARCHAR2(30) |
| FIRSTNAME | NOT NULL | VARCHAR2(20) |
| LASTNAME | (nullable) | VARCHAR2(30) |
| HIRE_DATE | (nullable) | DATE |
| JOB_TITLE | (nullable) | VARCHAR2(20) |
➕ Add a New Column
ALTER TABLE EMPLOYEE
ADD (BIRTH_DATE DATE);
✔️ Adds a new column `BIRTH_DATE` of type `DATE`.
✏️ Modify Column with Default Value
ALTER TABLE EMPLOYEE
MODIFY (LASTNAME DEFAULT 'LASTNAMEHERE');
✔️ Adds a default value `'LASTNAMEHERE'` for the `LASTNAME` column.
📏 Modify Data Type of an Existing Column
ALTER TABLE EMPLOYEE
MODIFY (FIRSTNAME VARCHAR2(35));
✔️ Expands the `FIRSTNAME` column from 20 to 35 characters in width.