Question

i’ve got this union query:

(SELECT INSTALLER, INSTALLTIME, RESULT, JOBNUMBER, HONAME, ADDRESS, CITY, STATE, ZIP, NOTES, SMNOTES, '' as priority, PAFS, upsell, TERM, MMRUPGRADE, WARRANTY, EFT FROM ACCOUNTS 
WHERE INSTALLDATE = '$date' && FUNDINGSTATUS !='DEAD') 
UNION 
(SELECT technician, servicetime, result, ID, Customername, address, city, state, zip, notes, board, priority, '', '', '', '', '', '' FROM service 
WHERE serviceday = '$date') 
ORDER BY INSTALLER, priority

i’m curious if putting an index on the date field will help speed up both queries? or will the fact that i use FUNDINGSTATUS in the first where clause will make that query not utilize the index?

Answer 1

Answering your very question:

I’m curious if putting an index on the date field will help speed up both queries?

If the condition on installdate and serviceday is selective (that is few rows satisfy it), then yes, it will help.

Date fields usually tend to be selective.

or will the fact that i use FUNDINGSTATUS in the first where clause will make that query not utilize the index?

Yes, the index will still be used.

The engine will use the index to select only the records with installdate = $date and the will additionally filter on the value of fundingstatus.

For best results, create the following indexes:

ACCOUNTS  (installdate, fundingstatus)
service (serviceday)

If DEAD is a frequent value for fundingstatus, it may be better to rewrite this query like this:

SELECT  INSTALLER, INSTALLTIME, RESULT, JOBNUMBER, HONAME, ADDRESS, CITY, STATE, ZIP, NOTES, SMNOTES, '' as priority, PAFS, upsell, TERM, MMRUPGRADE, WARRANTY, EFT
FROM    ACCOUNTS 
WHERE   INSTALLDATE = '$date' AND FUNDINGSTATUS < 'DEAD'
UNION ALL
SELECT  INSTALLER, INSTALLTIME, RESULT, JOBNUMBER, HONAME, ADDRESS, CITY, STATE, ZIP, NOTES, SMNOTES, '' as priority, PAFS, upsell, TERM, MMRUPGRADE, WARRANTY, EFT
FROM    ACCOUNTS 
WHERE   INSTALLDATE = '$date' AND FUNDINGSTATUS > 'DEAD'
UNION
SELECT  technician, servicetime, result, ID, Customername, address, city, state, zip, notes, board, priority, '', '', '', '', '', ''
FROM    service 
WHERE   serviceday = '$date'
ORDER BY
        INSTALLER, priority

so that the range access on both fields (installdate, fundingstatus) can be used.