SQL: How to create new columns depending on other column's value in the same table - sql

Question

I have 2 tables, Main and Units.
Main table:
Todate Unit CategoryID Quantity
1/7/2012 1 S 300
1/7/2012 1 U 350
2/7/2012 2 S 220
3/7/2012 2 S 50
3/7/2012 2 U 330
4/7/2012 1 S 200
4/7/2012 1 U 180
S = Sales, U = Upgrades
Units table:
UnitNum UnitName
1 Measures
2 Performance
I need to get this result:
Todate UnitNum UnitName Sales Upgrades
1/7/2012 1 Measures 300 350
2/7/2012 2 Performance 220
3/7/2012 2 Performance 50 330
4/7/2012 1 Measures 200 180
Meaning i need to create 2 columns - sales and upgrades, depending on the value in CategoryID, and i need them to be in the same row.
What i have so far is this
select Todate, Main.Unit, UnitName,
case when CategoryID = 'S' then Quantity end as Sales,
case when CategoryID = 'U' then Quantity end as Upgrades
from Main join Units on Main.UnitNum = Units.UnitNum
group by Todate, Main.Unit, UnitName
It gives me 2 new columns but they are in two separate rows..
I would really appreciate any help resolving this!
Thank you

Answer 1

You just need an aggregate query around the case statements.
select m.todate
, m.unit
, u.unitname
, sum(case when m.categoryid = 'S' then quantity end ) as sales
, sum(case when m.categoryid = 'U' then quantity end ) as upgrages
from main m
join units u
on m.unit = u.unitnum
group by m.todate, m.unit, u.unitname

Answer 2

You need something like this:
SELECT
Todate, m.Unit, UnitName,
Sales = (SELECT SUM(Quantity)
FROM dbo.Main m2
WHERE m.Todate = m2.Todate AND CategoryID = 'S'),
Updates = (SELECT SUM(Quantity)
FROM dbo.Main m2
WHERE m.Todate = m2.Todate AND CategoryID = 'U')
FROM
dbo.Main m
INNER join
dbo.Units u on m.Unit = u.UnitNum
GROUP BY
Todate, m.Unit, UnitName
ORDER BY
Todate, m.Unit, UnitName
This seems to be returning the output you're looking for:

Answer 3

You need to do a self-join of your main table with itself:
SELECT m1.todate, m1.unit AS unitnum, u.unitname,
SUM(m1.quantity) AS sales, SUM(m2.quantity) AS upgrades
FROM (SELECT todate, unit, quantity FROM Main WHERE category = 'S') AS m1
FULL OUTER JOIN
(SELECT todate, unit, quantity FROM Main WHERE category = 'U') AS m2
ON m1.todate = m2.todate AND m1.unit = m2.unit
JOIN units AS u
ON m1.unit = u.unitnum
GROUP BY m1.todate, m1.unit, u.unitname
ORDER BY m1.todate, m1.unit, u.unitname;
There are many other equivalent ways of writing the same query; this one preserves the symmetry of the problem fairly well, though. (Updated to use a FULL OUTER JOIN between the m1 and m2 sub-queries, to deal with cases where there are sales with no upgrades or upgrades with no sales.)

Answer 4

You could use PIVOT for this too:
WITH data AS (
SELECT
m.Todate,
m.UnitNum,
u.UnitName,
Category = CASE m.CategoryID
WHEN 'S' THEN 'Sales'
WHEN 'U' THEN 'Upgrades'
END,
Quantity
FROM Main m
INNER JOIN Units u
ON m.UnitNum = u.UnitNum
)
SELECT
Todate,
UnitNum,
UnitName,
Sales,
Upgrades
FROM data
PIVOT (
SUM(Quantity) FOR Category IN (Sales, Upgrades)
) p
;