询问一个sql语句

Question

select * from A
union all
select * from b
union all
select * from c
union all
select * from d

Answer 1

select * from a,b,c,d where a.col=b.col......or select * from a
union all
select * from b
union all
.....

Answer 2

select table1.col1,table1.col2,..table2.col1,table2.col2... from table1,table2,table3,table4

Answer 3

select table1.*,table2.*,table3.*,table4.* from table1,table2,table3,table4

Answer 4

select * from A
select * from b
select * from c
select * from d

Answer 5

最终解决办法：select * from A
select * from b
select * from c
select * from d