When should an outer join be preferred over an inner join in data queries?

An outer join is preferable when all records from one table need to be preserved, even if there are no matching records in the other table involved in the join. This type of join ensures that all entries from the specified table are included in the result set, alongside any matching records from the second table. If there is no corresponding match found, the result will still include the row from the first table, but with null values for the columns from the second table.

This characteristic of outer joins is particularly useful in scenarios where maintaining the integrity of the full dataset from one side is crucial for analysis or reporting, regardless of the existence of related records in the associated dataset. For instance, if you are working with a customer table and an order table, using an outer join could allow you to include all customers in your report, highlighting even those without any orders, which can be valuable for understanding customer engagement and retention.

In contrast, an inner join would only return rows with matching values from both tables, potentially excluding valuable information present in one of the datasets. The other choices do not align with the fundamental use case of outer joins, as they describe scenarios more suited to inner joins or other data manipulation techniques.