Combine two tables to display desired output - mysql

Question

I'm creating a query which will display projected qty versus qty sold on a monthly basis. Below are my two tables and third one is what i want as an output. The two table is almost the same, except that the date and creation date is in different format (i have converted this to output e.g 201301, so no worries about it).
As you have noticed in my output table, qty sold become 25.00 because it adds the qty if the date falls under the same month and year. I also need to consider these three important conditions:
to display rows with projected qty but without sales (ex. item 206)
To display rows without projected qty but with sales (ex. item 312)
to display row with projection and with sales (ex. item001 & 040)
I don't know if i have to used join or union to be able to achieve my desired output.
Table A (Sales Table)
item code Sold date
001 cust001 10.00 2013-01-20
001 cust001 15.00 2013-01-25
040 cust045 16.00 2013-04-07
312 cust001 20.00 2013-03-13
Table B (Projection Table)
item Custcode ProjectedQty Creation Date
001 cust001 20.00 2013-01-01
040 cust045 50.00 2013-04-01
206 cust121 60.00 2013-04-01
Output
item Custcode sold Date ProjectedQty Creation Date
001 cust001 25.00 201301 20.00 201301
312 cust001 20.00 201303 null null
040 cust045 16.00 201304 50.00 201304
206 cust121 null null 60.00 201304
Thanks guys for helping.

Answer 1

Try
SELECT COALESCE(p.item, s.item) item,
COALESCE(p.code, s.code) code,
sold,
CONCAT(s.year, LPAD(s.month, 2, '0')) date,
ProjectedQty,
CONCAT(p.year, LPAD(p.month, 2, '0')) creationdate
FROM
(
SELECT item, code, YEAR(`date`) year, MONTH(`date`) month
FROM sales
UNION
SELECT item, custcode, YEAR(`creationdate`), MONTH(`creationdate`)
FROM projection
) i LEFT JOIN
(
SELECT item, code, SUM(sold) sold, YEAR(`date`) year, MONTH(`date`) month
FROM sales
GROUP BY item, code, YEAR(`date`), MONTH(`date`)
) s ON i.item = s.item
AND i.code = s.code
AND i.year = s.year
AND i.month = s.month LEFT JOIN
(
SELECT item, custcode code, SUM(ProjectedQty) ProjectedQty, YEAR(`creationdate`) year, MONTH(`creationdate`) month
FROM projection
GROUP BY item, custcode, YEAR(`creationdate`), MONTH(`creationdate`)
) p ON i.item = p.item
AND i.code = p.code
AND i.year = p.year
AND i.month = p.month
ORDER BY code, item
Output:
| ITEM | CODE | SOLD | DATE | PROJECTEDQTY | CREATIONDATE |
------------------------------------------------------------------
| 001 | cust001 | 25 | 201301 | 20 | 201301 |
| 312 | cust001 | 20 | 201303 | (null) | (null) |
| 040 | cust045 | 16 | 201304 | 50 | 201304 |
| 206 | cust121 | (null) | (null) | 60 | 201304 |
SQLFiddle

Answer 2

Why not use a simple join for this?
SELECT * FROM `sales`, `projection` WHERE `code`=`custcode`;
Make a view of the query above, and using WHERE clause, you can alter the data.

Answer 3

Create a view using union. and then you can use the below query:
select *, sum(sold) as sold from view group by item
another is:
select *, sum(sold) from (
select item, code as Custcode, sold, date, 'ProjectedQty' as ProjectedQty, 'Creation Date' as Creation Date from table 1 union select item, Custcode, sold, Date, ProjectedQty, Creation Date, from table 2) group by item