Question

我编写了以下查询以获取id作为输入，从Attachment表中获取DocumentID，然后使用该id从Document表中获取Document name。一旦我得到文件名，我除去了字符a-z和数字。如果基于实体ID仅返回一个Document id，则下面的Query工作正常，如果一个实体id返回多个Document ID，我该如何使它工作。我还需要返回所有这些新名称。

ALTER PROCEDURE [dbo].[NormalizeDocumentFileName1] 
    -- Add the parameters for the stored procedure here
    @id nvarchar(16),
    @temp varchar(50) OUTPUT
AS
BEGIN

  Select @temp=Document.TheName from Document where id = (Select DocumentId from Attachment where EntityId = @id)
  Declare @KeepValues as varchar(50)
  Set @KeepValues = '%[^a-z0-9-_.]%'
  While PatIndex(@KeepValues, @temp) > 0
  Set @temp = Stuff(@temp, PatIndex(@KeepValues, @temp), 1, '')
   
END

Answer 1

就个人而言，我会采用一种截然不同的方法。我将使用Alan Burstein的NGrams8K。

你想避免WHILE循环，它会表现得非常好，并采用数据集方法。我将改为使用函数：

CREATE FUNCTION NormalizeDocumentFileName (@FileName varchar(50) )
RETURNS TABLE
AS RETURN

    WITH Tokens AS (
        SELECT *
        FROM dbo.NGrams8k (@FileName,1) --If you didn't create the function on the dbo schema, you'll need to change it.
        WHERE token NOT LIKE '%[^a-z0-9-_.]%')
    SELECT CONVERT(varchar(50),(SELECT Token + '' 
                                FROM Tokens
                                ORDER BY Position
                                FOR XML PATH(''))) AS NormalFileName;
GO

然后你可以做一些简单的事情：

SELECT D.YourColumn, NDFN.NormalFileName
FROM Document D
     CROSS APPLY NormalizeDocumentFileName(D.TheName) NDFN;

Answer 2

嗯。您可以省略while循环并使用递归CTE：

with cte as (
      Select d.TheName, 0 as lev, d.TheName as orig_TheName
      from Document d
      where d.id = (Select DocumentId from Attachment where EntityId = @id)
      union all
      select Stuff(cte.thename, PatIndex(@KeepValues, cte.thename), 1, '') as DocumentId lev + 1, cte.orig_TheName
      from cte
      where PatIndex(@KeepValues, cte.thename) > 0
     )
select theName
from (select theName, max(lev) over (partition by orig_thename) as max_lev
      from cte
     ) x
where lev = max_lev

Answer 3

这种类型的事物的另一个基于集合的函数是PatExclude8K，该函数与Larnu放在一起并且可重用的功能相同。您必须使用该链接获取T-SQL代码才能创建该功能。功能如下：

DECLARE @string varchar(50) = '$$$123___!!!555.ABC???';

SELECT * FROM dbo.patexclude8k(@string, '[^A-Za-z0-9-_.]');

返回：

NewString
------------
123___555.ABC

请注意，LARNU放在一起将返回XML字符的实体引用，例如“＆amp;”，“＆gt;”等。但它的效果会比Patexclude好。如果您不希望处理特殊的XML字符，您可以使用稍微修改后的版本，它将执行相对相同的操作 - 这就是：

CREATE FUNCTION dbo.PatExclude8K_NXP
(
    @String VARCHAR(8000),
    @Pattern VARCHAR(50)
) 
/*******************************************************************************
 Purpose:
 Given a string (@String) and a pattern (@Pattern) of characters to remove, 
 remove the patterned characters from the string.

Usage:
--===== Basic Syntax Example
 SELECT CleanedString 
 FROM dbo.PatExclude8K_NXP(@String,@Pattern);

--===== Remove all but Alpha characters
 SELECT CleanedString 
 FROM dbo.SomeTable st
 CROSS APPLY dbo.PatExclude8K(st.SomeString,'%[^A-Za-z]%');

--===== Remove all but Numeric digits
 SELECT CleanedString
 FROM dbo.SomeTable st
 CROSS APPLY dbo.PatExclude8K(st.SomeString,'%[^0-9]%');

 Programmer Notes:
 1. @Pattern is case sensitive (the function can be easily modified to make it so)
 2. There is no need to include the "%" before and/or after your pattern since since we 
    are evaluating each character individually

 Revision History:
 Rev 00 - 20180508 Initial Development - Alan Burstein

*******************************************************************************/
RETURNS TABLE WITH SCHEMABINDING AS
RETURN
WITH
E1(N) AS (SELECT N FROM (VALUES (NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL)) AS X(N)),
itally(N) AS 
(
  SELECT TOP(CONVERT(INT,LEN(@String),0)) ROW_NUMBER() OVER (ORDER BY (SELECT NULL))
  FROM E1 T1 CROSS JOIN E1 T2 CROSS JOIN E1 T3 CROSS JOIN E1 T4
) 
SELECT NewString =
(
  SELECT SUBSTRING(@String,N,1)
  FROM iTally
  WHERE 0 = PATINDEX(@Pattern,SUBSTRING(@String COLLATE Latin1_General_BIN,N,1))
  FOR XML PATH('')
);

最后，当优化器选择并行执行计划时，NGrams8K和PatExclude都会表现得更好。要强制执行并行计划，您可以使用Adam Machanic的Make_parallel。以Larnu的解决方案为例，您可以强制执行并行计划：

SELECT D.YourColumn, NDFN.NormalFileName
FROM Document D
     CROSS APPLY NormalizeDocumentFileName(D.TheName) NDFN;
     CROSS APPLY dbo.make_parallel();

SQL Query通过从其他表

3 个答案: