A better way to parse integer values from a T-SQL

问题:

I have a SQLServer2008 R2 Stored Procedure that contains an algorithm for parsing out integers from a delimited string.

Here's an example of the SQL code that I made for looping through the delimited string and extracting any numbers that may exist in the delimited string:

-- Create a delimited list for testing
DECLARE @NumericList nvarchar(MAX) = N'1, 33,44 ,55, foo ,666,77 77,8,bar,9,10'

-- Declare the delimiter
DECLARE @ListDelimiter VARCHAR(1) = ','

-- Remove white space from the list
SET @NumericList = REPLACE(@NumericList, ' ','');

-- Var that will hold the value of the delimited item during the while-loop
DECLARE @NumberInScope VARCHAR(MAX)

WHILE(LEN(@NumericList) > 0)
BEGIN
    -- Get the value to the left of the first delimiter.
    IF(CHARINDEX(@ListDelimiter, @NumericList) > 0)
        SET @NumberInScope = LEFT(@NumericList, CHARINDEX(@ListDelimiter, @NumericList))
    ELSE
        SET @NumberInScope = @NumericList   

    -- Remove the @NumberInScope value from the @NumericList
    SET @NumericList = RIGHT(@NumericList, LEN(@NumericList) - LEN(@NumberInScope))

    -- Remove the delimiter from the @NumberInScope
    SET @NumberInScope = REPLACE(@NumberInScope,@ListDelimiter,'')

    -- Print only the integer values
    IF(ISNUMERIC(@NumberInScope) = 1)
    BEGIN
        PRINT @NumberInScope
    END 
END

The code above works fine, but after reviewing the code it seems to me that there's got to be a more concise way of doing the same thing. In other words, is there any string functions (or any new R2 function, maybe) that I'm overlooking that I can implement that would shrink the code and, hopefully, be easier to read?

回答1:

Here is the code, you can also create a 'split' function and use that

DECLARE @NumericList nvarchar(max) = N'1, 33,44 ,55, foo ,666,77 77,8,bar,9,10'

;WITH cte as (
SELECT CAST(1 as bigint) p1,  CHARINDEX(',', @NumericList+',') p2, 
CAST(null as Nvarchar(max)) NumberInScope 
UNION ALL
SELECT p2 + 1, CHARINDEX(',',@NumericList+',', p2 + 1), 
SUBSTRING(@NumericList, p1, p2-p1) 
FROM cte WHERE p2>0
)
SELECT NumberInScope from cte WHERE isnumeric(NumberInScope) > 0
OPTION (MAXRECURSION 0)

回答2:

The definitive article is "Arrays and Lists in SQL Server 2005 and Beyond"

Here several methods are shown for splitting CSVs: CLR, Numbers table, WHILE loops

回答3:

From MSSql Server 2016, there is a new keyword introduced STRING_SPLIT to do the desired operation.

SELECT STRING_SPLIT ( string , separator )

Refer https://msdn.microsoft.com/en-us/library/mt684588.aspx