SELECT tbl_123.var_1, tbl_123.var_2, tbl_45.var_3, tbl_45.var_5
FROM
    (
	SELECT t3.var_3, t1.var_7, t2.var_6
	FROM tabla_1 t1
	INNER JOIN tabla_2 t2
		ON t2.var_1 = t1.var_1
	INNER JOIN tabla_3 t3
		ON t3.var_2 = t2.var_2
	WHERE t3.var_3 >= '2017-10-01'
     ) tbl_123

INNER JOIN

     (
   	SELECT t4.var_3, t4.var_6, t5.var_4, t5.var_5
	FROM tabla_4 t4
	INNER JOIN tabla_5 t5
		ON t5.var_4 = t4.var_4
	WHERE t4.var_3 >= '2017-10-01'
     ) tbl_45
  ON tbl_123.var_3 = tbl45.var_3 AND tbl_123.var_6 = tbl_45.var_6