F fix versioning bug

CHANGELOG.md

@@ -17,6 +17,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed ###
 
+* Bug in `retrieveOverrides` function where selecting the datatype of an old
+  version resultet in an error. See corresponding test in `caosdb-pyinttest`
+  `tests/test_versioning.py::test_datatype_without_name`
+
 ### Security ###
 
 ## 3.0.0 (2020-09-01) ##

procedures/retrieveEntityOverrides.sql

@@ -91,13 +91,11 @@ retrieveOverridesBody: BEGIN
                 NULL AS collection_override,
                 NULL AS name_override,
                 NULL AS desc_override,
-                ( SELECT value FROM
-                    ( SELECT value FROM name_data
-                        WHERE domain_id = 0
-                        AND entity_ID = datatypeID
-                        AND property_id = 20
-                        UNION SELECT datatype AS value
-                    ) AS tmp LIMIT 1 ) AS type_override,
+                IFNULL((SELECT value FROM name_data
+                    WHERE domain_id = 0
+                    AND entity_id = datatype
+                    AND property_id = 20
+                    LIMIT 1), datatype) AS type_override,
                 entity_id,
                 property_id
             FROM archive_data_type
@@ -154,10 +152,10 @@ retrieveOverridesBody: BEGIN
         NULL AS collection_override,
         NULL AS name_override,
         NULL AS desc_override,
-        ( SELECT value FROM name_data
+        IFNULL((SELECT value FROM name_data
             WHERE domain_id = 0
             AND entity_ID = datatype
-            AND property_id = 20 LIMIT 1 ) AS type_override,
+            AND property_id = 20 LIMIT 1), datatype) AS type_override,
         entity_id,
         property_id
     FROM data_type