How to resolve “Error saving the Query field.'fn_' is a reserved word and may not appear in your query” error?

The error “Error saving the Query field.'fn_' is a reserved word and may not appear in your query" is an SFMC error that occurs when a reserved word is being used in a Selection.

SFMC has a list of reserved words that are protected and cannot be used for naming conventions in SQL queries or other configurations. This ensures system integrity and prevents conflicts with internal operations.

The term "fn_" is one of the reserved words in Salesforce Marketing Cloud (SFMC) and cannot be removed from the system's Reserved Word Exceptions table. This restriction exists because SFMC does not support the use of user-defined functions within SQL queries, as highlighted in their SQL documentation.

For example: If you were trying to create a field with the name "fn_example" in your Data Extension, SFMC would prevent this due to the reservation of "fn_". Instead, you would need to choose a different naming convention, such as "function_example" or "custom_fn_example", to avoid conflicts.

How to resolve this?

The only workaround for this error is to either:

• Change the field name and avoid the usage of the reserved string
• Create a new field that replicates the value of the original one, so you can use it in the query - this workaround would prevent the modification of the original field, which can be handy if there are integrations defined with it.

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