The TRIM function removes either or both leading or trailing
    spaces, numbers, or characters from any character value
    expression. SQL returns the specified string minus any leading
    or trailing characters (or both).

    The BOTH option is the default if none is specified. The space
    character is the default if a string is not specified.

    The character value expression that you trim must be defined
    as data type CHAR, VARCHAR, NCHAR, or NCHAR VARYING. Use the
    CAST function to convert other data types before using the TRIM
    function.

    SQL returns a run-time error when the trim character is not
    exactly one character in length.

    Examples: Using the TRIM function

    Example 1: The following example, though not effective, shows the
    TRIM function:

    SQL> SELECT LAST_NAME,
    cont> TRIM (LEADING 'H' FROM LAST_NAME)
    cont> FROM EMPLOYEES
    cont> WHERE LAST_NAME LIKE 'H%';

     LAST_NAME
     Hall             all
     Harrington       arrington
     Harrison         arrison
     Hastings         astings
     Herbener         erbener
    5 rows selected

    Example 2: Using the TRIM function with the WHERE clause

    SQL> -- The following INSERT statement helps to show the
    SQL> -- TRIM function.
    SQL> --
    SQL> INSERT INTO EMPLOYEES (LAST_NAME,FIRST_NAME,EMPLOYEE_ID) VALUES
    cont> ('  Hillson','Ann','99999');
    1 row inserted
    SQL> --
    SQL> -- If you select columns without specifying the
    SQL> -- TRIM function on the WHERE clause, SQL returns only those
    SQL> -- last names that start with 'H' and have no leading spaces.
    SQL> --
    SQL> SELECT LAST_NAME || ', ' || FIRST_NAME
    cont> FROM EMPLOYEES
    cont> WHERE LAST_NAME LIKE 'H%';

     Hall          , Lawrence
     Harrington    , Margaret
     Harrison      , Lisa
     Hastings      , Norman
     Herbener      , James
    5 rows selected
    SQL> --
    SQL> -- Add the TRIM function to the WHERE clause to get a complete
    SQL> -- list of last names beginning with 'H' including those with
    SQL> -- leading spaces.
    SQL> --
    SQL> SELECT LAST_NAME || ', ' || FIRST_NAME
    cont> FROM EMPLOYEES
    cont> WHERE TRIM (LEADING ' ' FROM LAST_NAME) LIKE 'H%';

     Hastings      , Norman
     Harrington    , Margaret
     Hall          , Lawrence
     Harrison      , Lisa
       Hillson     , Ann
     Herbener      , James
    6 rows selected

    Example 3: Using the TRIM function on the SELECT portion of a
    query in addition to the WHERE clause

    SQL> -- Add the TRIM function to the SELECT portion of the query
    SQL> -- to trim the leading spaces from the display of 'Hillson'.
    SQL> -- Note that the LEADING option has been changed to the BOTH
    SQL> -- option to trim leading and trailing spaces from the
    SQL> -- LAST_NAME column.
    SQL> --
    SQL> SELECT TRIM (BOTH ' ' FROM LAST_NAME) || ', ' || FIRST_NAME
    cont> FROM EMPLOYEES
    cont> WHERE TRIM (LEADING ' ' FROM LAST_NAME) LIKE 'H%';

     Hastings, Norman
     Harrington, Margaret
     Hall, Lawrence
     Harrison, Lisa
     Hillson, Ann
     Herbener, James
    6 rows selected