Question

一条sql语句

oracle中一张表test，有id，a，b 3个字段，选出a=1或b=2的所有记录，a=1且b=2的排在最前面，a=1且b=2的记录按id降序排列。

Answer 1

select * from test where a=1 and b=2
union
select * from test where a=1 or b= 2 order by a,b asc,id desc

Answer 2

select id,a,b
from test
where a=1 and b=2
order by id desc
union
select id,a,b
from test
where a=1 or b=2

Answer 3

select * from test t where t.a=1 and t.b=2 order by t.id desc;

a=1且b=2排在最前面是什么意思？你查a=1且b=2就全是满足这个条件的数据啦，还要怎么排最前面？

Answer 4

select * from test where a=1 and b=2 order by desc

Answer 5

select id,a,b from test where a=1 and b=2;