Omitting a join condition is a subtle, yet classic blunder. Do so, and you're guaranteed not to get the results you intended.


This rule raises an issue when a table is included in the ``++FROM++`` list but not in the ``++WHERE++`` list in relation to other tables, and when only part of a compound key is used in the conditions.


== Noncompliant Code Example

[source,text]
----
SELECT p.name, f.name
FROM product p, 
  product_feature f  -- Noncompliant
WHERE p.id=?

SELECT p.name, ck.date
FROM product p
JOIN compound_key_table ck
  ON p.manufacturer_product_id=ck.manufacturer_product_id  -- Noncompliant
WHERE ...
----


== Compliant Solution

[source,text]
----
SELECT p.name, f.name
FROM product p, 
  product_feature f
WHERE p.id=f.product_id AND p.id=?

SELECT p.name, ck.date
FROM product p
JOIN compound_key_table ck
  ON p.manufacturer_product_id=ck.manufacturer_product_id AND p.manufacturer_id=ck.manufacturer_id
WHERE ...
----