If the WHERE clause uses CURRENT OF cursor-name, SQL modifies
    only the row on which the named cursor is positioned. The cursor
    named in an UPDATE statement must meet these conditions:

    o  The cursor must have been named previously in a DECLARE CURSOR
       statement or FOR statement.

    o  The cursor must be open.

    o  The cursor must be on a row.

    o  The FROM clause of the SELECT statement within the DECLARE
       CURSOR statement must refer to the table or view that is the
       target of the UPDATE statement.