How to Efficiently Parse Comma-Separated Strings for SQL IN Clauses?

Handling Comma-Separated Strings in SQL Queries

Many database operations require input parameters as lists. When these lists are provided as comma-separated strings, converting them to a SQL-compatible format is crucial.

The Challenge:

Consider a stored procedure receiving a comma-separated string like this:

<code class="language-sql">DECLARE @Account AS VARCHAR(200)
SET @Account = 'SA,A'</code>

The goal is to transform this string into a usable SQL IN clause:

<code class="language-sql">WHERE Account IN ('SA', 'A')</code>

A High-Performance Solution:

A user-defined function offers the most efficient approach. This function splits the comma-separated string into a table:

<code class="language-sql">CREATE function [dbo].[f_split]
(
@param nvarchar(max), 
@delimiter char(1)
)
returns @t table (val nvarchar(max), seq int)
as
begin
set @param += @delimiter

;with a as
(
select cast(1 as bigint) f, charindex(@delimiter, @param) t, 1 seq
union all
select t + 1, charindex(@delimiter, @param, t + 1), seq + 1
from a
where charindex(@delimiter, @param, t + 1) > 0
)
insert @t
select substring(@param, f, t - f), seq from a
option (maxrecursion 0)
return
end</code>

This function is then used within the SQL query:

<code class="language-sql">SELECT *
FROM yourtable 
WHERE account in (SELECT val FROM dbo.f_split(@account, ','))</code>

Why This Method Is Superior:

Compared to alternatives like XML parsing, this function provides:

• Exceptional Performance: Significantly faster than XML-based methods.
• Reusability: Easily adaptable to various applications.
• Simplicity: Avoids complex string manipulation.

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