add G-3182, closes #197

Author: PhilippSalvisberg

docs/4-language-usage/3-dml-and-sql/1-general/g-3182.md

@@ -0,0 +1,36 @@
+# G-3182: Always specify column names instead of positional references in GROUP BY clauses.
+
+!!! bug "Blocker"
+    Reliability
+
+## Restriction
+
+Oracle Database 23c
+
+## Reason
+
+If you use a numeric literal in the `group by` clause in an Oracle Database prior to version 23c, then this literal is not required. It is simply a constant.
+
+Starting with Oracle Database 23c, it is possible to use a literal in the `group by` clause to refer to a column name in the `select` list. However, this only works if the `group_by_position_enabled` parameter is set to `true`. In any case, it is not convenient for the readers of the code to have to count the columns in the `select` list to know how the result is grouped.
+
+Since the meaning of a `literal` depends on the configuration and database version, the intention is unclear and might lead to an incorrect result.
+
+## Example (bad)
+
+``` sql
+select job_id
+      ,sum(salary) as sum_salary
+  from employees
+ group by job_id,2 -- violates also G-1050
+ order by job_id;
+```
+
+## Example (good)
+
+``` sql
+select job_id
+      ,sum(salary) as sum_salary
+  from employees
+ group by job_id
+ order by job_id;
+```