Leftrimming Zero与字符串中包含的字符与字符

Question

我需要编写一个函数，从varchar列中删除所有前导零。例如：0300必须变为300，A0300必须变成A300。第一个退出容易，但我不能得到第二个工作（A0300-> A300）。任何人都可以将我指向正确的方向吗？

Answer 1

WITH test AS 
(
    SELECT 'A0300' AS code 
    UNION 
    SELECT '0300' 
), 
strip AS (
SELECT code, SUBSTRING(code, PATINDEX('%[0-9]%', code), LEN(code)) AS number 
from test 
) 

select REPLACE(code, number, CAST(number as INT)) 
FROM strip 

Answer 2

在旧版本，其中PATINDEX不起作用，或者如果PATINDEX太慢：

做的情况下，并使用LIKE '[0-9]'/ NOT LIKE '[0-9]'找到正确的分裂点 - 假设知道您的字符串的最大长度，以便您可以根据需要准备多个案例。 您可以在数字开头找到正确的字符编号，并将右边的部分作为INT进行转义以消除前导0，然后将结果作为VARCHAR进行转换，以重新汇总您的前导字母。

会制造类似如下： 选择 CASE WHEN LEFT（列名，1）NOT LIKE '[0-9]' 和substring（列名，2,1）LIKE '[0-9]' 然后离开（ （列名，2）（LEN（columnname）-2））AS INT）AS VARCHAR（25）） 当左（列名，2）不像'[0-9]'和底层（columnname，3,1）.... END

如果您不确定前导/尾随空格，您应该用LTRIM（RTRIM（columnname））修剪空格，因为我们要计算字符可能更可靠。

Answer 3

下面的溃烂代码演示了一种方式，用一个平凡的状态机遍历字符串，并解析出邪恶的零。要查看内部发生了什么，可以在CTE之后切换select。

-- Sample data. 
declare @Samples as Table (SampleId Int Identity, Sample VarChar(100)); 
insert into @Samples (Sample) values 
    ('0300'), ('A0300'), ('zer0'), ('0'), ('000'), ('00000Q050098'); 
select * from @Samples; 

-- Fiendish thingy. 
declare @False as Bit = 0, @True as Bit = 1; 
with 
    Characters as (
    select SampleId, Sample, 1 as Position, Substring(Sample, 1, 1) as Character, 
     case when Substring(Sample, 1, 1) = '0' then @True else @False end as IsZero, 
     case when Substring(Sample, 1, 1) = '0' then @True else @False end as FirstZeroes 
     from @Samples 
    union all 
    select SampleId, Sample, Position + 1, Substring(Sample, Position + 1, 1), 
     case when Substring(Sample, Position + 1, 1) = '0' then @True else @False end, 
     case 
     when FirstZeroes is NULL then NULL -- We're done with this string. 
     when FirstZeroes = @True and Substring(Sample, Position + 1, 1) <> '0' then NULL -- We just finished with this string. 
     when Substring(Sample, Position + 1, 1) = '0' then @True -- We're (still) going with this string. 
     else @False end 
     from Characters 
     where Position < Len(Sample)) 
-- select * from Characters order by SampleId, Position; -- Use this statement to see the intermediate results. 
    select C.SampleId, C.Sample, 
    Coalesce(Stuff((select Character from Characters where SampleId = C.SampleId and (FirstZeroes = 0 or FirstZeroes is NULL) order by Position for XML path(''), type).value('.[1]', 'VarChar(max)'), 1, 0, ''), '') as DeZeroed 
    from Characters as C 
    group by SampleId, Sample