fix sql merge syntax for iceberg

dlt/destinations/sql_jobs.py

@@ -100,17 +100,17 @@ def gen_key_table_clauses(cls, root_table_name: str, staging_root_table_name: st
 
             A list of clauses may be returned for engines that do not support OR in subqueries. Like BigQuery
         """
-        return [f"FROM {root_table_name} as d WHERE EXISTS (SELECT 1 FROM {staging_root_table_name} as s WHERE {' OR '.join([c.format(d='d',s='s') for c in key_clauses])})"]
+        return [f"FROM {root_table_name} WHERE EXISTS (SELECT 1 FROM {staging_root_table_name} as s WHERE {' OR '.join([c.format(d=root_table_name,s='s') for c in key_clauses])})"]
 
     @classmethod
-    def gen_delete_temp_table_sql(cls, unique_column: str, key_table_clauses: Sequence[str]) -> Tuple[List[str], str]:
+    def gen_delete_temp_table_sql(cls, unique_column: str, key_table_clauses: Sequence[str], root_table_name: str) -> Tuple[List[str], str]:
         """Generate sql that creates delete temp table and inserts `unique_column` from root table for all records to delete. May return several statements.
 
            Returns temp table name for cases where special names are required like SQLServer.
         """
         sql: List[str] = []
         temp_table_name = cls._new_temp_table_name("delete")
-        select_statement = f"SELECT d.{unique_column} {key_table_clauses[0]}"
+        select_statement = f"SELECT {root_table_name}.{unique_column} {key_table_clauses[0]}"
         sql.append(cls._to_temp_table(select_statement, temp_table_name))
         for clause in key_table_clauses[1:]:
             sql.append(f"INSERT INTO {temp_table_name} SELECT {unique_column} {clause};")
@@ -184,7 +184,7 @@ def gen_merge_sql(cls, table_chain: Sequence[TTableSchema], sql_client: SqlClien
             # get first unique column
             unique_column = sql_client.capabilities.escape_identifier(unique_columns[0])
             # create temp table with unique identifier
-            create_delete_temp_table_sql, delete_temp_table_name = cls.gen_delete_temp_table_sql(unique_column, key_table_clauses)
+            create_delete_temp_table_sql, delete_temp_table_name = cls.gen_delete_temp_table_sql(unique_column, key_table_clauses, root_table_name)
             sql.extend(create_delete_temp_table_sql)
             # delete top table
             sql.append(f"DELETE FROM {root_table_name} WHERE {unique_column} IN (SELECT * FROM {delete_temp_table_name});")