Select quantity of record instances separated by weeks - mysql

Question

I have a table like the below:
CompanyID | Logged | UniqueID
A | 2014-06-24 | 8
B | 2014-06-24 | 7
A | 2014-06-16 | 6
B | 2014-06-16 | 5
A | 2014-06-08 | 4
B | 2014-06-08 | 3
A | 2014-06-01 | 2
B | 2014-06-01 | 1
I'm stuck trying to create an SQL statement that will return the quantity of rows found for each unique CompanyID, separated into 4 week periods, so something like the below:
CompanyID | Period (week) | Quantity
A | 0 | 1
B | 0 | 1
A | 1 | 1
B | 1 | 1
A | 2 | 1
B | 2 | 1
A | 3 | 1
B | 3 | 1
I have done something similar before, except by the last 7 days instead of last 4 weeks, but am not sure if this can be reworked:
select CompanyID,
case DATE_FORMAT(Logged, '%Y%m%d')
when '20140618' then '0'
when '20140619' then '1'
when '20140620' then '2'
when '20140621' then '3'
when '20140622' then '4'
when '20140623' then '5'
when '20140624' then '6'
end as period ,
count(UniqueID) as quantity from TABLE
where DATE_FORMAT(Logged, '%Y%m%d')
in (20140618,20140619,20140620,20140621,20140622,20140623,20140624) group by CompanyID,
DATE_FORMAT(Logged, '%Y%m%d')
Is there a more straightforward way to obtain the output desired above?

Answer 1

Maybe something like this?
SQL FIDDLE to test with
Theres the original query that doesn't use any hard coding... that is generally a really bad practice. it will have the count inflated by 1 since it starts with one and you want it to start with zero so to fix this do a select of the original query where you fix the count and then also not show the user defined variable
SELECT CompanyID, Period - 1 as Period, Quantity FROM(
SELECT
CompanyID,
if(#a = Logged, #b, #b := #b + 1) as Period,
COUNT(*) as Quantity,
#a := Logged
FROM test
JOIN (SELECT #a := '', #b := 0) as temp
GROUP BY UniqueID
ORDER BY Period
) as subQuery
ORIGINAL QUERY
SELECT
CompanyID,
if(#a = Logged, #b, #b := #b + 1) as Period,
COUNT(*) as Quantity,
#a := Logged
FROM test
JOIN (SELECT #a := '', #b := 0) as temp
GROUP BY UniqueID
ORDER BY Period