sql语句的问题!

Question

select Field,OtherField from(
select Field,OtherField,a Name from table
where Field<=3
union all
select Field,OtherField,b Name  from table
where Field>3 and Field<=6
union all
select Field,OtherField,c Name  from table
where Field>6)
group by Name

Answer 1

SQL> select id,case when id>0 and id<6 then 1 else 2 end case from test;        ID       CASE
---------- ----------
         1          1
         2          1
         5          1
         4          1
         5          1
         6          2
         8          2
         9          2
        10          2
         6          2
         8          2        ID       CASE
---------- ----------
         9          2
        10          2
         7          2

Answer 2

select decode(sign(field-4),-1,1,
       decode(sign(field-7),-1,2,
       decode(sign(field-11),-1,3,0))) from tablename;最后一个零表示字段值不在[1~10]之间

Answer 3

select decode(sign(field-1)*sign(3-field),1,1,decode(sign(field-4)*sign(6-field),1,2,decode(sign(field-7)*sign(10-filed),1,3))) from tabname