Omit external volume from DDL when not provided (#1192)

Co-authored-by: Colin Rogers <[email protected]>

Author: dlouseiro

dbt-snowflake/.changes/unreleased/Fixes-20250718-092225.yaml

@@ -0,0 +1,6 @@
+kind: Fixes
+body: Omit external volume from DDL when not provided in the YAML file
+time: 2025-07-18T09:22:25.851623+02:00
+custom:
+    Author: dlouseiro
+    Issue: "772"

dbt-snowflake/src/dbt/adapters/snowflake/relation.py

@@ -209,10 +209,11 @@ def get_iceberg_ddl_options(self, config: RelationConfig) -> str:
 
         external_volume = config.get("external_volume")  # type:ignore
         iceberg_ddl_predicates: str = f"""
-        external_volume = '{external_volume}'
         catalog = 'snowflake'
         base_location = '{base_location}'
         """
+        if external_volume := config.get("external_volume"):  # type:ignore
+            iceberg_ddl_predicates += f"\nexternal_volume = '{external_volume}'"
         return textwrap.indent(textwrap.dedent(iceberg_ddl_predicates), " " * 10)
 
     def __drop_conditions(self, old_relation: "SnowflakeRelation") -> Iterator[Tuple[bool, str]]: