My sql , join tables with dynamic fields

i want to use @mm as global scope var and use it value in second and 3rd tables.(even dummy field to join ) anyone has idea? thanks

select a.totalL,b.totalR, @mm:=c.plac from users as c inner join (SELECT SUM(amnt) as totalL ,type,@mm as MN FROM gb WHERE amnt> 0 AND plac_id LIKE concat(@mm,'1%')

AND (DATE(date1) BETWEEN DATE('2015-06-23 00:00:00') AND DATE('2015-08-13 23:59:59') ) AND type=10 ) as a on c.plac = a.MN inner join (SELECT SUM(amnt) as totalR ,type,@mm as MN FROM gb WHERE amnt> 0 AND plac_id LIKE concat(@mm,'2%') AND (DATE(date1) BETWEEN DATE('2015-06-23 00:00:00') AND DATE('2015-08-13 23:59:59') ) AND type=10 )as b on a.type = b.type

via Chebli Mohamed