What are the Limitations of SQL Server's IN Clause and How Can They Be Overcome?

Understanding the Limitations of the IN Clause in SQL Server

When working with the IN clause in SQL Server, it's important to be aware of its limitations with regards to the number of values that can be included in its expression list.

Is there a specific limit?

Microsoft acknowledges the existence of a limit but provides a vague indication that it is "in the thousands". This means that queries with thousands of comma-separated values in the parentheses of the IN clause may encounter issues.

What are the consequences?

Exceeding this limit can lead to errors, such as 8623 or 8632. These errors highlight that the query complexity exceeds available resources or involves an excessive number of tables or partitions.

How to work around the limit?

To avoid these errors, you can store the items in the IN list in a separate table and use a SELECT subquery within the IN clause instead. This approach reduces the complexity of the query and prevents resource exhaustion.

Additional information

It's worth noting that the limit applies not only to the IN clause but to query complexity as a whole. Complex expressions or queries referencing a large number of tables or partitions can also trigger errors 8623 or 8632.

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