If I understand your question, you will need a query that utilizes
sub-queries and
inner join to generate the appropriate resulting table. I think it would be something similar to this:
SELECT
tbl1.itemcode,
tbl1.T1Quantity,
tbl2.T2Quantity,
(tbl1.T1Quantity - tbl2.T2Quantity) AS Variance
FROM
( SELECT
itemcode,
qty AS T1Quantity
FROM
table1
) AS tbl1 INNER JOIN
( SELECT
itemcode,
SUM(qty) AS T2Quantity
FROM
table2
GROUP BY
itemcode
) AS tbl2 ON tbl1.itemcode = tbl2.itemcode
[EDIT: version without subqueries in FROM clause]
SELECT
Table1.itemcode,
Table1.qty AS T1Quantity,
SUM(Table2.qty) AS T2Quantity,
Table1.qty - SUM(Table2.qty) AS Variance
FROM
Table1 INNER JOIN
Table2 ON Table1.itemcode = Table2.itemcode
GROUP BY
Table1.itemcode,
Table1.qty