Example 1: Specifying a comment for columns and tables

    SQL> -- Change the comment for the WORK_STATUS table:
    SQL> COMMENT ON TABLE WORK_STATUS IS
    cont> 'Links a status code with 1 of 3 statuses' ;
    SQL> SHOW TABLE WORK_STATUS
    Information for table WORK_STATUS

    Comment on table WORK_STATUS: Links a status code with 1 of 3 statuses
       .
       .
       .
    SQL> -- Create a comment for the DEPARTMENT_CODE
    SQL> -- column in the DEPARTMENTS table:
    SQL> COMMENT ON COLUMN DEPARTMENTS.DEPARTMENT_CODE IS
    cont> 'Also used in JOB_HISTORY table';
    SQL> SHOW TABLE DEPARTMENTS
    Information for table DEPARTMENTS

    Comment on table DEPARTMENTS:
    information about departments in corporation

    Columns for table DEPARTMENTS:
    Column Name                     Data Type        Domain
    -----------                     ---------        ------
    DEPARTMENT_CODE                 CHAR(4)          DEPARTMENT_CODE_DOM
     Comment:       Also used in JOB_HISTORY table
       .
       .
       .

    Example 2: Specifying a comment containing more than one string
    literal

    SQL> COMMENT ON COLUMN EMPLOYEES.EMPLOYEE_ID IS
    cont> '1: Used in SALARY_HISTORY table as Foreign Key constraint' /
    cont> '2: Used in JOB_HISTORY table as Foreign Key constraint';
    SQL> SHOW TABLE (COL) EMPLOYEES;
    Information for table EMPLOYEES

    Columns for table EMPLOYEES:
    Column Name                     Data Type        Domain
    -----------                     ---------        ------
    EMPLOYEE_ID                     CHAR(5)          ID_DOM
     Comment:       1: Used in SALARY_HISTORY table as Foreign Key constraint
                    2: Used in JOB_HISTORY table as Foreign Key constraint
     Primary Key constraint EMPLOYEES_PRIMARY_EMPLOYEE_ID
    LAST_NAME                       CHAR(14)         LAST_NAME_DOM
    FIRST_NAME                      CHAR(10)         FIRST_NAME_DOM
    MIDDLE_INITIAL                  CHAR(1)          MIDDLE_INITIAL_DOM
    ADDRESS_DATA_1                  CHAR(25)         ADDRESS_DATA_1_DOM
    ADDRESS_DATA_2                  CHAR(20)         ADDRESS_DATA_2_DOM
    CITY                            CHAR(20)         CITY_DOM
    STATE                           CHAR(2)          STATE_DOM
    POSTAL_CODE                     CHAR(5)          POSTAL_CODE_DOM
    SEX                             CHAR(1)          SEX_DOM
    BIRTHDAY                        DATE VMS         DATE_DOM
    STATUS_CODE                     CHAR(1)          STATUS_CODE_DOM

    Example 3: Adding a Comment to a Trigger

    SQL> COMMENT ON TRIGGER EMPLOYEE_ID_CASCADE_DELETE IS
    cont> 'When an employee is deleted from EMPLOYEES, delete'/
    cont> 'corresponding records from the other tables in the'/
    cont> 'database.';
    SQL> SHOW TRIGGER EMPLOYEE_ID_CASCADE_DELETE
         EMPLOYEE_ID_CASCADE_DELETE
      Source:
     EMPLOYEE_ID_CASCADE_DELETE
                        BEFORE DELETE ON EMPLOYEES
                        (DELETE FROM DEGREES D WHERE D.EMPLOYEE_ID =
                         EMPLOYEES.EMPLOYEE_ID)
                           FOR EACH ROW
                        (DELETE FROM JOB_HISTORY JH WHERE JH.EMPLOYEE_ID =
                         EMPLOYEES.EMPLOYEE_ID)
                           FOR EACH ROW
                        (DELETE FROM SALARY_HISTORY SH WHERE SH.EMPLOYEE_ID =
                         EMPLOYEES.EMPLOYEE_ID)
                           FOR EACH ROW
                      -- Also, if an employee is terminated and that employee
                      -- is the manager of a department, set the manager_id
                      -- null for that department.
                        (UPDATE DEPARTMENTS D  SET D.MANAGER_ID = NULL
                         WHERE D.MANAGER_ID = EMPLOYEES.EMPLOYEE_ID)
                           FOR EACH ROW.
       .
       .
       .
    Comment:       When an employees is deleted from EMPLOYEES, delete
                   corresponding records from the other tables in the
                   database.

    Example 4: Adding Comments to Multiple Columns in a Table

    SQL> COMMENT ON JOBS (JOB_CODE is 'Required column',
    cont> WAGE_CLASS is 'Valid values are: 1, 2, 3, or 4');
    SQL> SHOW TABLE (COLUMNS) JOBS;
    Information for table JOBS
    Columns for table JOBS:
    Column Name                     Data Type        Domain
    -----------                     ---------        ------
    JOB_CODE                        CHAR(4)          JOB_CODE
     Comment:       Required column
     Missing Value: None
    WAGE_CLASS                      CHAR(1)          WAGE_CLASS
     Comment:       Valid values are: 1, 2, 3, or 4
    JOB_TITLE                       CHAR(20)         JOB_TITLE
     Missing Value: None
    MINIMUM_SALARY                  INTEGER(2)       SALARY
    MAXIMUM_SALARY                  INTEGER(2)       SALARY