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Join three tables mySQL

Posted on 2011-03-11
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Last Modified: 2012-05-11
I want to join three tables: anestheticrecord, patient and anesthmedsgiven

anestheticrecord and patient share the field 'PatNum'
anestheticrecord and anesthmedsgiven share the field 'AnestheticRecordNum'

I've tried the following:

SELECT anestheticrecord.AnestheticRecordNum,anestheticrecord.AnestheticDate,
patient.PatNum as 'Patient #',patient.LName,patient.FName,patient.Gender,patient.Birthdate,patient.Address,patient.Address2,patient.City,patient.Zip,
patient.HmPhone,patient.WirelessPhone,anesthmedsgiven.AnesthMedName,anesthmedsgiven.QtyGiven,anesthmedsgiven.QtyWasted
FROM anestheticrecord,patient,anesthmedsgiven
WHERE ((anestheticrecord.PatNum = patient.PatNum) AND (anesthmedsgiven.AnestheticRecordNum = anestheticrecord.AnestheticRecordNum))
AND DATE_FORMAT(anestheticdate,'%Y-%m-%d') >= '2011-01-01' AND DATE_FORMAT(anestheticdate,'%Y-%m-%d') <= '2011-03-11'

which returns no results. I don't think I can use 2 LEFT JOINS because the three tables don't share a foreign key.

Any suggestions?
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Question by:wjstarck
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Accepted Solution

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DrivingInstructor earned 500 total points
ID: 35113940
It is quite possible to use 2 left joins for this. The first left join uses the shared key between anestheticrecord and patient while the second left join uses the shared key between anestheticrecord and anesthmedsgiven thus:

 
SELECT * FROM anestheticrecord AS a
LEFT JOIN patient AS p (p.PatNum = a.PatNum)
LEFT JOIN anesthmedsgiven AS m (m.AnestheticRecordNum = a.AnestheticRecordNum)

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May not seem real, and may break best practices, I don't know, but I know it can be done as I have done it.
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Author Closing Comment

by:wjstarck
ID: 35113994
Yes, that does work after all. Thanks.
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