Why Is Using '*' in View Definitions Considered a Pitfall?

The Pitfalls of Using '*' in View Definitions

Understanding the Problem

Consider the following scenario: you have a complex join with numerous fields, each of which may be used in various contexts. To optimize performance, you may want to create a view that contains all the relevant fields using the wildcard (*) operator:

CREATE VIEW aview AS
SELECT *
FROM table1
INNER JOIN table2
...

However, this approach can lead to problems if two fields share the same name across the joined tables. This can cause ambiguity and unexpected results when querying the view.

A Deeper Dive

While this is one reason why using '*' in view definitions is discouraged, there are additional concerns:

• Context Reliance: Views that use '*' make it easier to access fields that may not be relevant to the current context. This can lead to unexpected behavior and performance issues.
• Schema Changes: If the underlying tables undergo schema changes (e.g., addition or removal of columns), views that rely on '*' may remain valid but may no longer provide the intended information. Explicitly naming the selected columns would make schema changes more apparent and facilitate necessary adaptations.

An Alternative Perspective

It's important to note that there may be scenarios where using '*' in view definitions is intentionally desirable. For instance, if you want a view to automatically adapt to changes in the underlying schema, a wildcard definition might be suitable. However, it's crucial to carefully consider the potential drawbacks and implement appropriate safeguards to avoid unintended consequences.

Conclusion

While using '*' in view definitions can sometimes appear convenient, it's generally advisable to explicitly specify the required fields. This approach provides greater clarity, avoids ambiguity, and enhances the maintainability and reliability of your database views.

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