嗨，我有一个视图，该视图在我的应用程序中的许多搜索查询中都使用过。 问题是使用此视图的应用程序查询运行非常缓慢。我正在对此进行调查，发现在视图定义中有一个特定的部分正在使其运行缓慢。 创建视图Demoview AS
Select
p.Id as Id,
----------,
STUFF((SELECT ',' + [dbo].[OnlyAlphaNum](colDesc)
FROM dbo.ContactInfoDetails cd
WHERE pp.FormId = f.Id AND ppc.PageId = pp.Id
FOR XML PATH('')), 1, 1, '') AS PhoneNumber,
p.FirstName as Fname,
From
---
这是视图中的列之一。
标量函数[OnlyAlphaNum]使其变慢，因为它停止了并行执行查询。
功能如下；
CREATE FUNCTION [dbo].[OnlyAlphaNum]
(
@String VARCHAR(MAX)
)
RETURNS VARCHAR(MAX)
WITH SCHEMABINDING
AS
BEGIN
WHILE PATINDEX('%[^A-Z0-9]%', @String) > 0
SET @String = STUFF(@String, PATINDEX('%[^A-Z0-9]%', @String), 1, '')
RETURN @String
END
如何将其转换为内联函数？ 我尝试使用CASE，但未成功。我已阅读到CTE是一个不错的选择。 知道如何解决这个问题吗？？
答案 0 :(得分：1)
我已经做到了；您可以详细了解here。
功能：
CREATE FUNCTION dbo.alphaNumericOnly8K(@pString varchar(8000))
RETURNS TABLE WITH SCHEMABINDING AS RETURN
/****************************************************************************************
Purpose:
Given a varchar(8000) string or smaller, this function strips all but the alphanumeric
characters that exist in @pString.
Compatibility:
SQL Server 2008+, Azure SQL Database, Azure SQL Data Warehouse & Parallel Data Warehouse
Parameters:
@pString = varchar(8000); Input string to be cleaned
Returns:
AlphaNumericOnly - varchar(8000)
Syntax:
--===== Autonomous
SELECT ca.AlphaNumericOnly
FROM dbo.AlphaNumericOnly(@pString) ca;
--===== CROSS APPLY example
SELECT ca.AlphaNumericOnly
FROM dbo.SomeTable st
CROSS APPLY dbo.AlphaNumericOnly(st.SomeVarcharCol) ca;
Programmer's Notes:
1. Based on Jeff Moden/Eirikur Eiriksson's DigitsOnlyEE function. For more details see:
http://www.sqlservercentral.com/Forums/Topic1585850-391-2.aspx#bm1629360
2. This is an iTVF (Inline Table Valued Function) that performs the same task as a
scalar user defined function (UDF) accept that it requires the APPLY table operator.
Note the usage examples below and see this article for more details:
http://www.sqlservercentral.com/articles/T-SQL/91724/
The function will be slightly more complicated to use than a scalar UDF but will yeild
much better performance. For example - unlike a scalar UDF, this function does not
restrict the query optimizer's ability generate a parallel query plan. Initial testing
showed that the function generally gets a
3. AlphaNumericOnly runs 2-4 times faster when using make_parallel() (provided that you
have two or more logical CPU's and MAXDOP is not set to 1 on your SQL Instance).
4. This is an iTVF (Inline Table Valued Function) that will be used as an iSF (Inline
Scalar Function) in that it returns a single value in the returned table and should
normally be used in the FROM clause as with any other iTVF.
5. CHECKSUM returns an INT and will return the exact number given if given an INT to
begin with. It's also faster than a CAST or CONVERT and is used as a performance
enhancer by changing the bigint of ROW_NUMBER() to a more appropriately sized INT.
6. Another performance enhancement is using a WHERE clause calculation to prevent
the relatively expensive XML PATH concatentation of empty strings normally
determined by a CASE statement in the XML "loop".
7. Note that AlphaNumericOnly returns an nvarchar(max) value. If you are returning small
numbers consider casting or converting yout values to a numeric data type if you are
inserting the return value into a new table or using it for joins or comparison
purposes.
8. AlphaNumericOnly is deterministic; for more about deterministic and nondeterministic
functions see https://msdn.microsoft.com/en-us/library/ms178091.aspx
Usage Examples:
--===== 1. Basic use against a literal
SELECT ao.AlphaNumericOnly
FROM samd.alphaNumericOnly8K('xxx123abc999!!!') ao;
--===== 2. Against a table
DECLARE @sampleTxt TABLE (txtID int identity, txt varchar(100));
INSERT @sampleTxt(txt) VALUES ('!!!A555A!!!'),(NULL),('AAA.999');
SELECT txtID, OldTxt = txt, AlphaNumericOnly
FROM @sampleTxt st
CROSS APPLY samd.alphaNumericOnly8K(st.txt);
---------------------------------------------------------------------------------------
Revision History:
Rev 00 - 20150526 - Inital Creation - Alan Burstein
Rev 00 - 20150526 - 3rd line in WHERE clause to correct something that was missed
- Eirikur Eiriksson
Rev 01 - 20180624 - ADDED ORDER BY N; now performing CHECKSUM conversion to INT inside
the final cte (digitsonly) so that ORDER BY N does not get sorted.
****************************************************************************************/
WITH
E1(N) AS
(
SELECT N
FROM (VALUES (NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL))x(N)
),
iTally(N) AS
(
SELECT TOP (LEN(ISNULL(@pString,CHAR(32)))) ROW_NUMBER() OVER (ORDER BY (SELECT NULL))
FROM E1 a CROSS JOIN E1 b CROSS JOIN E1 c CROSS JOIN E1 d
)
SELECT AlphaNumericOnly =
(
SELECT SUBSTRING(@pString,CHECKSUM(N),1)
FROM iTally
WHERE
((ASCII(SUBSTRING(@pString,CHECKSUM(N),1)) - 48) & 0x7FFF) < 10
OR ((ASCII(SUBSTRING(@pString,CHECKSUM(N),1)) - 65) & 0x7FFF) < 26
OR ((ASCII(SUBSTRING(@pString,CHECKSUM(N),1)) - 97) & 0x7FFF) < 26
ORDER BY N
FOR XML PATH('')
);
请注意代码注释中的示例：
--===== 1. Basic use against a literal
SELECT ao.AlphaNumericOnly
FROM samd.alphaNumericOnly8K('xxx123abc999!!!') ao;
--===== 2. Against a table
DECLARE @sampleTxt TABLE (txtID int identity, txt varchar(100));
INSERT @sampleTxt(txt) VALUES ('!!!A555A!!!'),(NULL),('AAA.999');
SELECT txtID, OldTxt = txt, AlphaNumericOnly
FROM @sampleTxt st
CROSS APPLY samd.alphaNumericOnly8K(st.txt);
返回：
AlphaNumericOnly
-------------------
xxx123abc999
txtID OldTxt AlphaNumericOnly
----------- ------------- -----------------
1 !!!A555A!!! A555A
2 NULL NULL
3 AAA.999 AAA999
这是同类产品中最快的。使用并行执行计划，它运行起来特别快。要强制执行并行执行计划，请获取make_parallel by Adam Machanic的副本。然后，您将像这样运行它：
--===== 1. Basic use against a literal
SELECT ao.AlphaNumericOnly
FROM dbo.alphaNumericOnly8K('xxx123abc999!!!') ao
CROSS APPLY dbo.make_parallel();
--===== 2. Against a table
DECLARE @sampleTxt TABLE (txtID int identity, txt varchar(100));
INSERT @sampleTxt(txt) VALUES ('!!!A555A!!!'),(NULL),('AAA.999');
SELECT txtID, OldTxt = txt, AlphaNumericOnly
FROM @sampleTxt st
CROSS APPLY dbo.alphaNumericOnly8K(st.txt)
CROSS APPLY dbo.make_parallel();
答案 1 :(得分：0)
当然有改进的空间。进行测试。
;WITH CTE AS (
SELECT (CASE WHEN PATINDEX('%[^A-Z0-9]%', D.Name) > 0
THEN STUFF(D.Name, PATINDEX('%[^A-Z0-9]%', D.Name), 1, '')
ELSE D.NAME
END ) NameString
FROM @dept D
UNION ALL
SELECT STUFF(C.NameString, PATINDEX('%[^A-Z0-9]%', C.NameString), 1, '')
FROM CTE C
WHERE PATINDEX('%[^A-Z0-9]%', C.NameString) > 0
)
Select STUFF((SELECT ',' + E.NameString from CTE E
WHERE PATINDEX('%[^A-Z0-9]%', E.NameString) = 0
FOR XML PATH('')), 1, 1, '') AS NAME