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Asked: 2026-05-25T06:52:03+00:00

I have about thirty strings that get passed to my stored procedure which act

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I have about thirty strings that get passed to my stored procedure which act as the columns of a table I need to manipulate. Each string is delimited and I use a split function to break each one of these strings apart into it’s appropriate rows which usually consist of twenty or fewer rows. The split function is quite fast and return a table result with one column being an ID which is the primary key and the other column being the split out value, and from examining the execution plan the thirty splits only take up a fraction of my time. The part that seems to kill my performance is the actual join among those thirty split results sets.

DECLARE @WorkingTab TABLE ([ID] INT PRIMARY KEY, [Col1] VARCHAR(255), [Col2] VARCHAR(255), ...)

INSERT INTO @WorkingTab ([ID], [Col1], [Col2], ...)
SELECT
    splitStr1.ID,
    splitStr1.VALUE,
    splitStr2.VALUE,
    .
    .
    .
FROM
    dbo.Split(@Str1, '~') splitStr1
    LEFT JOIN
        dbo.Split(@Str2, '~') splitStr2
    ON splitStr1.ID = splitStr2.ID
    LEFT JOIN
        dbo.Split(@Str3, '~') splitStr3
    .
    .
    .

I’ve tried using inner joins instead of left join which decreased performance slightly. I’ve tried inserting just the first split result into an indexed temp table then updating the rest of the column values into the appropriate column in the temp table which again resulted in a minor performance decrease. I’ve tried tried inserting all of the results into a persistent table which also didn’t improve performance at all. If anyone has any suggestions on other ways to approach this or just general performance tips, I’m all ears. Thanks in advance.

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1 Answer

  1. Editorial Team

    This is really not a good strategy, performance-wise. User defined functions will never be high performers. Have you considered submitting your data as an XML document and parsing it in a stored procedure? I’ve done that before and it’s usually a decent performer.

    In regards to your actual question, there may be some ability to optimize your table valued function so that it returns a table variable with a primary key defined, which could improve performance, but really, I recommend changing your upload strategy.

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