select result_list from ta where cond1
union
select result_list from tb where cond2
union
select result_list from tc where cond3
union
select result_list from td where cond4--result_list的字段个数与类型要一致
union
select result_list from tb where cond2
union
select result_list from tc where cond3
union
select result_list from td where cond4--result_list的字段个数与类型要一致
union all
select 字段1,字段2 from 表b where 字段1='关键字'
union all
select 字段1,字段2 from 表c where 字段1='关键字'
union all
select 字段1,字段2 from 表d where 字段1='关键字'