Fix #26 - Created rule G-3185 Never use ROWNUM at the same query level as ORDER BY.

Author: kibeha

docs/4-language-usage/3-dml-and-sql/1-general/g-3185.md

@@ -0,0 +1,40 @@
+# G-3185: Never use ROWNUM at the same query level as ORDER BY.
+
+!!! warning "Major"
+    Reliability, Testability
+
+## Reason
+
+The `rownum` pseudo-column is assigned before the `order by` clause is used, so using `rownum` on the same query level as `order by` will not assign numbers in the desired ordering. Instead you should move the `order by` into an inline view and use `rownum` in the outer query.
+
+## Example (bad)
+
+``` sql
+select first_name
+      ,last_name
+      ,salary 
+      ,hire_date
+      ,rownum as salary_rank
+  from employees
+ where rownum <= 5
+ order by salary desc;
+```
+
+## Example (good)
+
+``` sql
+select first_name 
+      ,last_name 
+      ,salary 
+      ,hire_date 
+      ,rownum as salary_rank
+  from (
+   select first_name 
+         ,last_name 
+         ,salary 
+         ,hire_date 
+     from employees
+    order by salary desc
+       )
+ where rownum <= 5;
+```