SQL Server将字符串转换为数字并进行排序

Question

I am attempting to sort a column of strings, which contains one alphanumeric character and a numbers. If I run this:

select 
    column_name 
from 
    table_name 
where 
    item_type = 'ABC' 
    and item_sub_type = 'DEF' 
order by 
    cast(replace([column_name], 'A', '') as Numeric(10, 0)) desc

I get the correct sorted output:

A218
A217
A216

but if I try to grab the top row

select top 1 
    column_name 
from 
    table_name 
where 
    item_type = 'ABC' 
    and item_sub_type = 'DEF' 
order by 
    cast(replace([column_name], 'A', '') as numeric(10, 0)) desc

it fails with the following error:

Error converting data type varchar to numeric

Any ideas on how I can select the top row?

Thanks!

Answer 1

I think this is the problem with your data - not all are match your pattern. You can check what is not valid using:

select column_name from table_name where ISNUMERIC(replace([column_name],'A','')) = 0

Answer 2

I think this is the optimizer not executing your query how you would hope. What I mean is SQL is a declarative language--your query merely states what you are trying to accomplish, not how you are trying to accomplish it (in most cases). Thus, the optimizer determines the best way and in cases as yours, does things in certain order that causes errors. Try and force your logic with a CTE.

with cte as(
select column_name, [item_value] 
from table_name 
where item_type='ABC' and item_sub_type='DEF')

select top 1 column_name
from cte 
ORDER BY CAST(replace([item_value],'A','') AS Numeric(10,0)) desc

SQL Server 2012/2016

select top 1 column_name 
from table_name 
where item_type='ABC' and item_sub_type='DEF' 
order by TRY_CONVERT(Numeric(10,0),replace([column_name],'A','')) desc

Answer 3

Order by dropping the prefix and casting to int, provided that the prefix is the only non-numeric the rest should be pure numbers.

select 
    column_name 
from 
    table_name 
where 
    item_type = 'ABC' 
    and item_sub_type = 'DEF' 
order by 
    cast(replace([column_name], 'A', '') as Int) desc

the script above should just work, i reckon there is something wrong with your data could multiple values...

see example below

declare @mytable table
(
code varchar(10) 
)

insert into @mytable
values 
('A323'),
('A223'),
('A123'),
('A553'),
('A923'),
('A23'),
('A235')



select 
    code
from 
    @mytable 
order by 
    cast(replace(code, 'A', '') as Int) desc


code
----------
A923
A553
A323
A235
A223
A123
A23