how to write code table1 into table2

[Guest]

dear member,
I want to write result comparison table1 between table2 and result must
write in table2.
1-table1 has item1 and qty1
2-table2 has item2, quatity2 and result

"when item1 = item2 then qty1 = quatity2 and result must write in column
result in table2."
any body can help me

 

[Guest]

may be you all understand what i mean;

statement;
if (item=item) then
result = qty1 - qty2

I has 2 table.
i want to write the result in table 2.

(what declaration database and record table need to write)