Specifies the position of the entry within the ACL. If you omit
    the AFTER or POSITION argument, SQL searches the entire ACL
    for an identifier list that matches the one specified in the
    FROM clause of the REVOKE statement. If it finds a match, it
    modifies the ACL entry by deleting the privileges specified in
    the privilege list. If there is no match, SQL generates an error
    and the REVOKE statement has no effect on the ACL.

    With the AFTER or POSITION argument, you can specify the position
    in the list from which SQL searches for an ACL entry with an
    identifier that matches the one specified in the FROM clause of
    the REVOKE statement.

    o  In the AFTER argument, the identifier specifies the entry in
       the ACL after which SQL begins its search for the entry to be
       modified or deleted. If none of the entries in the ACL has an
       identifier that matches the identifier specified in the AFTER
       argument, SQL generates an error and the statement fails.

       Starting after the entry specified by the identifier in the
       AFTER argument, SQL searches entries in the ACL. If an entry
       has an identifier that matches the identifier specified by the
       FROM clause of the REVOKE statement, SQL modifies or deletes
       that ACL entry.

       If none of the entries has an identifier that matches the
       identifier specified by the FROM clause of the REVOKE
       statement, SQL generates an error and the statement fails
       (even if an entry before the position at which SQL began its
       search had an identifier that matched).

       Specifying PUBLIC is equivalent to a wildcard specification of
       all user identifiers.

    o  In the POSITION argument, the integer specifies the earliest
       relative position in the ACL of the entry to be modified or
       deleted. If the integer is larger than the number of entries
       in the ACL, SQL generates an error and the statement fails.

       Starting with the position specified by the POSITION argument,
       SQL searches entries in the ACL. If an entry has an identifier
       that matches the identifier specified by the FROM clause of
       the REVOKE statement, SQL modifies or deletes that ACL entry.

       If none of the entries has an identifier that matches the
       identifier specified by the FROM clause of the REVOKE
       statement, SQL generates an error and the statement fails
       (even if an entry before the position at which SQL began its
       search had an identifier that matched).