fix: ml.sql logic (#262)

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Author: GarrettWu

bigframes/ml/sql.py

@@ -153,14 +153,12 @@ def create_model(
  ) -> str:
  """Encode the CREATE OR REPLACE MODEL statement for BQML"""
  source_sql = source_df.sql
- transform_sql = self.transform(*transforms) if transforms is not None else None
- options_sql = self.options(**options)
 
  parts = [f"CREATE OR REPLACE MODEL {self._model_id_sql(model_ref)}"]
- if transform_sql:
- parts.append(transform_sql)
- if options_sql:
- parts.append(options_sql)
+ if transforms:
+ parts.append(self.transform(*transforms))
+ if options:
+ parts.append(self.options(**options))
  parts.append(f"AS {source_sql}")
  return "\n".join(parts)
 
@@ -189,11 +187,10 @@ def create_imported_model(
  options: Mapping[str, Union[str, int, float, Iterable[str]]] = {},
  ) -> str:
  """Encode the CREATE OR REPLACE MODEL statement for BQML remote model."""
- options_sql = self.options(**options)
 
  parts = [f"CREATE OR REPLACE MODEL {self._model_id_sql(model_ref)}"]
- if options_sql:
- parts.append(options_sql)
+ if options:
+ parts.append(self.options(**options))
  return "\n".join(parts)