求SQL

Question

Table A
DHHM ZH
ASL00418204 232
ASL00384145 12
ASL00402638 232
ASL00409863 3
ASL00267635 23Table B
DHHM ZH
LAN00224731 ds要求出现
DHHM ZH
ASL00418204 232
LAN00224731 ds
ASL00384145 12
ASL00402638 232
ASL00409863 3
ASL00267635 23

Answer 1

select * from a 
union
select * from b

Answer 2

select   *   from   a   where DHHM ='ASL00418204 '
union 
select   *   from   b
union
select   *   from   a where DHHM <>'ASL00418204'