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7.2 Views and the Rule System

Views in PostgreSQL are implemented using the rule system. In fact, there is essentially no difference between:

CREATE VIEW myview AS SELECT * FROM mytab;

compared against the two commands:

CREATE TABLE myview (same column list as mytab);
CREATE RULE "_RETURN" AS ON SELECT TO myview DO INSTEAD
    SELECT * FROM mytab;

because this is exactly what the CREATE VIEW command does internally. This has some side effects. One of them is that the information about a view in the PostgreSQL system catalogs is exactly the same as it is for a table. So for the parser, there is absolutely no difference between a table and a view. They are the same thing: relations.