mysql - 添加两个独立表的SUM

Question

我有两张 table

td_sell

|----------|----------------|------------------|
|  id      |   user_id      |    price         |
|----------------------------------------------|
|  1       |      2         |     10           |
|----------------------------------------------|
|  2       |      1         |      5           |
|----------------------------------------------|
|  3       |      2         |      3           |
|----------------------------------------------|

和 td_commsion

|----------|----------------|------------------|
|  id      |   user_id      |    price         |
|----------------------------------------------|
|  1       |      1         |      3           |
|----------------------------------------------|
|  2       |      1         |      5           |
|----------------------------------------------|
|  3       |      2         |      3           |
|----------------------------------------------|

现在我想要一个像这样的sql查询

SELECT (SUM(td_sell.price) + SUM(td_comission.price)) AS his_earning
FROM td_sell, td_comission 
WHERE td_sell.user_id='1'
AND td_comission.user_id='1'

但显示异常结果

结果应该是 13，但显示的是 29

Answer 1

这会起作用:

SELECT (SELECT SUM(s.price) FROM td_sell s WHERE s.user_id = 1)
+
(SELECT SUM(c.price) FROM td_comission c WHERE c.user_id = 1)

演示:SqlFiddle