The rename operation

The rename operation is used to alter the attribute name of the resultant relation or to give a specific name to the resultant relation. The rename operation is used to perform the following:

• Remove confusion if two or more relations have attributes with the same name
• Provide user-friendly names for attributes, especially when interfacing with reporting engines
• Provide a convenient way to change the relation definition and still be backward compatible

The AS keyword in SQL is the equivalent of the rename operator in relational algebra. The following SQL example creates a relation with one tuple and one attribute, which is renamed PI:

SELECT 3.14::real AS PI;