Using 2 worksheets to calculate in sql - mysql

Question

I have data that goes back to 2004 to deal with so have to simplify calculations moving from using Excel to using SQL to save processing time & pressure on our servers.
My data is:
Period Employee EmOrg EmType Total Hours Mode
201306 GOVINP1 RSA/PZB/T00 S 180 66
201306 LANDCJ1 RSA/PZB/T00 S 200 35
201306 WOODRE RSA/PZB/T00 S 180 34
201306 MOKOHM1 RSA/JNB/T00 S 160 33
201306 KAPPPJ RSA/PLZ/T00 S 160 32
201306 CAHISJ RSA/PZB/T00 S 187 31
201306 ZEMUN RSA/PZB/T00 S 180 31
201306 SAULDD1 RSA/PZB/T00 S 190 28
201306 JEROP1 RSA/DUR/T00 S 188 26
201306 NGOBS1 RSA/PZB/T00 S 204 24
201306 ZONDNS2 RSA/PZB/T00 S 192 23
201306 DLAMMP RSA/PZB/T00 S 201 23
201306 MPHURK RSA/PLZ/T00 S 160 22
201306 MNDAMB RSA/PZB/T00 S 188 21
My desired outcome is:
Period EmOrg EmType TotalHours FTE S
201308 RSA/BFN/T00 S 198 1
201308 RSA/CPT/T00 S 744 3.757575
201308 RSA/DUR/T00 S 805 4.065656
201308 RSA/JNB/T00 S 396 2
201308 RSA/PLZ/T00 S 563 2.843434
201308 RSA/PTA/T00 S 594 3
201308 RSA/PZB/T00 S 4882 24.656565
And my query:
SELECT
LD.Period,
LD.EmOrg,
LD.EmType,
Sum(LD.RegHrs) AS 'Total Hours',
Sum(LD.RegHrs) / 198 As 'FTE_S'
FROM
SSI.dbo.LD LD
GROUP BY LD.Period , LD.EmOrg , LD.EmType
HAVING (LD.EmOrg Like '%T00')
AND (LD.EmType = 'S')
How do I refer to a column in a different worksheet to use as my Mode rather than dividing with an actual number? Because different months have a different mode and using an actual number will give wrong output in other months.

Answer 1

You need to create a separate table for your Mode per month and than use JOIN to get that value and use it.
Something like this:
SELECT
LD.Period,
LD.EmOrg,
LD.EmType,
Sum(LD.RegHrs) AS 'Total Hours',
Sum(LD.RegHrs) / M.Mode As 'FTE_S'
FROM
SSI.dbo.LD LD
INNER JOIN SSI.dbo.Mode M
ON LD.Period = M.Period -- Not sure its should be Period or Month
GROUP BY LD.Period , LD.EmOrg , LD.EmType
HAVING (LD.EmOrg Like '%T00')
AND (LD.EmType = 'S')