普及数据库order by语句

Question

我有以下SQL语句：

select * 
from
    (select  
         id,
         left(id, 6) as Hauptnummer,
         convert(substring(id, 8), SQL_BIGINT) as Detailnummer
     from 
         Proben 
     where 
         id like '%-%'  
         and id like '2%' 
         and length(id) > 7) as a 
order by  
    Hauptnummer desc, Detailnummer

当我运行这条语句时，我得到以下错误：

表达式错误

不使用ORDER BY子句即可正确执行该语句。

如何编写此ORDER BY子句？

Answer 1

您正在尝试按在子查询之外的字段排序。让我们尝试相同的代码(下面是MS SQL的语法)：

/* declare and create temp (in-memory) table */
declare @proben table
(
    id nvarchar(24)
)

/* insert come test data to table */
insert @proben(id) values('2345-67890')
insert @proben(id) values('54654645-6257890')
insert @proben(id) values('2345-67890546541')
insert @proben(id) values('4355343542345-67890')

/* check of select of your script */
select *
from (
    select
        id,
        left(id, 6) as Hauptnummer,
        CAST(substring(id, 8, 0) AS BIGINT) as Detailnummer
    from
        @proben
    where
        id like '%-%'
        and id like '2%'
        and len(id) > 7
    order by
        Hauptnummer desc, Detailnummer
    ) as a
order by
    a.Hauptnummer desc, a.Detailnummer

Answer 2

如果在SQL-Server(T-SQL)中使用的代码可以使用以下代码来实现: Substring函数接受字符转换，因此代码已按以下方式重写。子串函数的语法：SUBSTRING(string, start, length)

例如：

select * 
from
    (select  
        id,
        left(id, 6) as Hauptnummer, 
        substring(convert (varchar(20), id ), 1, 2) as Detailnummer 
     from 
        Proben 
     where 
        id like '%-%'  
        and id like '2%'  
        and len(id) > 7) as a  /* SQL server it is len instead length */
order by  
    Hauptnummer desc, Detailnummer