Question

DECLARE
          v_count NUMBER ;
        begin
            SELECT Count(COMPLETION) INTO v_count  FROM AIMS  WHERE  Code=997 AND completion !=2  ;
            IF v_count = 0 THEN
               UPDATE UNITS pu
                    SET
                      code = 'COM',
                      status = 'F',
                      by = '',
                      date =     (
                          SELECT Nvl(Max(la.end_date), To_Date('01/01/1900', 'DD/MM/YYYY'))
                          FROM aims la  WHERE la.code = 997  GROUP BY la.code  
                          ) ;  
                      WHERE ID = 997 ;
            END IF ;

             END;

Answer 1

You have an extra semi-colon in your code. Remove the semi colon here:

                  date =     (
                      SELECT Nvl(Max(la.end_date), To_Date('01/01/1900', 'DD/MM/YYYY'))
                      FROM aims la  WHERE la.code = 997  GROUP BY la.code  
                      ) ;