How Can I Efficiently Search for Values Within Comma-Delimited Strings in SQL Server?

Locating Specific Values in Comma-Separated SQL Server Columns

Working with SQL Server 2008, you might need to find rows where a particular value resides within a column containing comma-separated values. The challenge lies in locating this value anywhere within the string, not just as an exact string match.

Let's examine this problem:

• Sample Table:

  <code class="language-sql">  CREATE TABLE DelimitedValues (id INT, ColumnName VARCHAR(100));
    INSERT INTO DelimitedValues VALUES
    (1, 'Cat,Dog,Sparrow,Trout,Cow,Seahorse'),
    (2, 'Mouse');</code>

• Objective: Identify rows where ColumnName includes specific values like "Cat" or "Sheep".

Standard methods like IN fall short because they don't handle values embedded within the comma-separated lists. A more sophisticated approach is necessary.

A powerful solution uses string concatenation and the LIKE operator:

<code class="language-sql">SELECT id
FROM DelimitedValues
WHERE (',' + RTRIM(ColumnName) + ',') LIKE '%,' + @search + ',%'</code>

This technique ensures the search value (@search) is surrounded by commas, enabling detection regardless of its position within the list. For instance:

• ColumnName holds 'Cat,Dog,Sparrow,Trout,Cow,Seahorse'
• @search is 'Cat'
• Result: Row 1 is returned because 'Cat' is found within the comma-delimited string.

This method reliably handles all cases: values at the beginning, middle, or end of the list, and single-value entries.

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