49 lines
1.2 KiB
Plaintext
49 lines
1.2 KiB
Plaintext
== Why is this an issue?
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``++NATURAL JOIN++`` is a type of equi-join which implicitly compares all identically-named columns of the two tables. While this a feature which may seem convenient at first, it becomes hard to maintain over time.
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Consider an EMPLOYEE table with the columns FULL_NAME, and DEPT_ID, and a DEPARTMENT table with the columns DEPT_ID, and NAME. A natural join between those tables will join on the DEPT_ID column, which is the only identically-named column.
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But, if a new NAME column is later added to the EMPLOYEE table, then the join will be done on both DEPT_ID and NAME. Natural joins make simple changes such as adding a column complicated and are therefore better avoided.
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=== Noncompliant code example
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[source,sql]
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----
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BEGIN
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SELECT *
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INTO employeeArray
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FROM employee
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NATURAL JOIN departement; -- Non-Compliant, the join predicate is implicit
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END;
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/
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----
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=== Compliant solution
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[source,sql]
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----
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BEGIN
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SELECT *
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INTO employeeArray
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FROM employee
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JOIN departement
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USING (dept_id); -- Compliant, explicit join predicate
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END;
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/
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----
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ifdef::env-github,rspecator-view[]
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'''
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== Implementation Specification
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(visible only on this page)
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include::message.adoc[]
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endif::env-github,rspecator-view[]
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