feat(v_ahb_diff): indicate which columns were actually modified

README.md

@@ -216,24 +216,24 @@ create_ahb_diff_view(session)
 ```
 
 Die View erwartet 4 Filter-Parameter beim Abfragen und liefert einen `diff_status`:
-- `added`: Zeile existiert in Version A, aber nicht in Version B
-- `deleted`: Zeile existiert in Version B, aber nicht in Version A
-- `modified`: Zeile existiert in beiden Versionen, aber mit unterschiedlichen Werten
+- `added`: Zeile existiert in der neuen Version, aber nicht in der alten
+- `deleted`: Zeile existiert in der alten Version, aber nicht in der neuen
+- `modified`: Zeile existiert in beiden Versionen, aber mit unterschiedlichen Werten (bei `modified` enthält `changed_columns` die Liste der geänderten Spalten)
 - `unchanged`: Zeile ist in beiden Versionen identisch
 
-Alle Wert-Spalten existieren doppelt (`_a` und `_b`), um die Werte aus beiden Versionen nebeneinander anzuzeigen.
+Alle Wert-Spalten existieren doppelt (`old_*` und `new_*`), um die Werte aus beiden Versionen nebeneinander anzuzeigen.
 
 ```sql
 -- Alle Änderungen zwischen zwei Versionen anzeigen
-SELECT path, diff_status,
-       segment_ahb_status_a, segment_ahb_status_b,
-       dataelement_ahb_status_a, dataelement_ahb_status_b,
-       code_value_a, code_value_b
+SELECT path, diff_status, changed_columns,
+       old_line_ahb_status, new_line_ahb_status,
+       old_bedingung, new_bedingung,
+       old_line_name, new_line_name
 FROM v_ahb_diff
-WHERE format_version_a = 'FV2504'
-  AND format_version_b = 'FV2410'
-  AND pruefidentifikator_a = '55014'
-  AND pruefidentifikator_b = '55014'
+WHERE old_format_version = 'FV2410'
+  AND new_format_version = 'FV2504'
+  AND old_pruefidentifikator = '55014'
+  AND new_pruefidentifikator = '55014'
   AND diff_status != 'unchanged'
 ORDER BY sort_path;
 ```

src/fundamend/sqlmodels/ahb_diff_view.py

@@ -95,6 +95,10 @@ class AhbDiffLine(SQLModel, table=True):
     # Diff status: 'added', 'deleted', 'modified', 'unchanged'
     diff_status: str = Field()
 
+    # Which columns changed (for modified rows only, NULL otherwise)
+    # Comma-separated list, e.g. 'line_ahb_status, bedingung'
+    changed_columns: Optional[str] = Field(default=None)
+
     # Old version columns (from v_ahbtabellen)
     old_segmentgroup_key: Optional[str] = Field(default=None)
     old_segment_code: Optional[str] = Field(default=None)

src/fundamend/sqlmodels/create_ahb_diff_view.sql

@@ -42,6 +42,21 @@ SELECT
         THEN 'modified'
         ELSE 'unchanged'
     END AS diff_status,
+    CASE
+        WHEN COALESCE(old_tbl.line_ahb_status, '') != COALESCE(new_tbl.line_ahb_status, '')
+          OR COALESCE(old_tbl.bedingung, '') != COALESCE(new_tbl.bedingung, '')
+          OR COALESCE(old_tbl.line_name, '') != COALESCE(new_tbl.line_name, '')
+        THEN
+            TRIM(
+                CASE WHEN COALESCE(old_tbl.line_ahb_status, '') != COALESCE(new_tbl.line_ahb_status, '')
+                     THEN 'line_ahb_status, ' ELSE '' END ||
+                CASE WHEN COALESCE(old_tbl.bedingung, '') != COALESCE(new_tbl.bedingung, '')
+                     THEN 'bedingung, ' ELSE '' END ||
+                CASE WHEN COALESCE(old_tbl.line_name, '') != COALESCE(new_tbl.line_name, '')
+                     THEN 'line_name' ELSE '' END
+            , ', ')
+        ELSE NULL
+    END AS changed_columns,
     new_tbl.id_path AS id_path,
     new_tbl.sort_path AS sort_path,
     new_tbl.path AS path,
@@ -82,6 +97,7 @@ UNION ALL
 -- Added rows (exist in new but not in old for the specific version pair)
 SELECT
     'added' AS diff_status,
+    NULL AS changed_columns,
     new_tbl.id_path,
     new_tbl.sort_path,
     new_tbl.path,
@@ -124,6 +140,7 @@ UNION ALL
 -- Deleted rows (exist in old but not in new for the specific version pair)
 SELECT
     'deleted' AS diff_status,
+    NULL AS changed_columns,
     old_tbl.id_path,
     old_tbl.sort_path,
     old_tbl.path,