code: def join_query_data(target, source):
      if len(target.columns) == 0:
          target = source
      else:
          target.add_records(source.get_records())
      return target
  
file_path: mindsdb/mindsdb/api/executor/sql_query/steps/map_reduce_step.py
imports: import copy
  from mindsdb_sql.parser.ast import BinaryOperation, UnaryOperation, Constant
  from mindsdb_sql.planner.steps import MapReduceStep, FetchDataframeStep, MultipleSteps
  from mindsdb.api.executor.sql_query.result_set import ResultSet
  from mindsdb.api.executor.exceptions import LogicError
  from .base import BaseStepCall
  from .fetch_dataframe import FetchDataframeStepCall
label_desc: Use image node_id 4 for calling a global function with example usage: join_query_data(target, source) and returns: target