使用 select 语句创建的字段上出现无效标识符错误

Question

为什么下面的sql不起作用？

select
    a.field1, a.field2, a.field3,
    (select count(*)
        from table2 b
        where b.field1 = a.field1
    ) as field4,
    (select count(*)
        from table3 b
        where b.field1 = a.field1
    ) as field5,
    (select count(*)
        from table4 b
        where b.field1 = a.field1
    ) as field6,
from table1 a
order by field4

Oracle 说：ORA-00904：“field4”：无效标识符

Answer 1

尝试把它包起来

select * from 
(    
select
    a.field1, a.field2, a.field3,
    (select count(*)
        from table2 b
        where b.field1 = a.field1
    ) as field4,
    (select count(*)
        from table3 b
        where b.field1 = a.field1
    ) as field5,
    (select count(*)
        from table4 b
        where b.field1 = a.field1
    ) as field6,
from table1 a
)
order by field4