Summing data from 2 or more tables in a pivot table

[VL126]

Hi,

I have 2 tables that are in diff shapes (diff number of columns) but they do have common fields like below :

Table 1	Field A	Field B	Field C	Field D	Field E	Field F	Field G	10 other columns
Table 2	Field A	Field B	Field C	Field D	Field E	Field F	Field G	5 other columns

What i want to do is to create a pivot table which add up the value field (say field G) from the 2 tables. My pivot table would be something like this :

2 Row Dimensions : Field A and Field B

3 Column Dimensions : Field C/D/E

Value : sum of Field G from 2 tables

Pivot Table		Column
			Field C
			Field D
			Field E
Row	Row
Field A	Field B		Sum of Field G from 2 tables

I tried having associate say using Field A of the 2 tables to build the pivot and in the measure expression I used Sum (field G) Table 1 + Sum of field G Table2. What I notice is, say if Field A could have 3 diff values, the for value 1 of Field A, the Field G presented with some numbers. When scroll down further, value 2 of Field A got exactly  the same numbers in the pivot as per value 1 above. Same happen for value 3 under field A. 

Could anyone advise me what went wrong?