mysql数据库sum问题，求大神帮忙？？？？？？？？？

Question

我想查询两个表中不同属性值的和，放在一条查询语句中，出现结果翻倍问题！
sql语句如下：
select
sum(lcb_in_money.IN_MONEY)
,sum(lcb_out_money.OUT_MONEY) from
lcb_in_money,lcb_out_money
where 
lcb_in_money.USER_ID = lcb_out_money.USER_ID =1;
输出结果如下：
+---------------------------------------------------------------+-----------------------------------------------------------------+
 |                 sum(lcb_in_money.IN_MONEY)           |           sum(lcb_out_money.OUT_MONEY)            |
+---------------------------------------------------------------+-----------------------------------------------------------------+
 |                                           12                                      |                                               66                                    |
+----------------------------------------------------------------+----------------------------------------------------------------+
真实结果应该为6和33，整整翻了一倍，求大神指教？？？？？？？？？

Answer 1

select
sum(lcb_in_money.IN_MONEY)
,sum(lcb_out_money.OUT_MONEY) from
lcb_in_money,lcb_out_money
where 
lcb_in_money.USER_ID = lcb_out_money.USER_ID
and   lcb_out_money.USER_ID=1;