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complex mysql join for dataassist results page

Thread began 6/16/2011 2:07 pm by Jenny I | Last modified 6/20/2011 4:52 pm by Jason Byrnes | 1431 views | 7 replies |

Jenny I

complex mysql join for dataassist results page

Hi

I am currently struggling to understand how I can get some values from a complex mysql join.

The values I am trying to get are people.firstname and people.lastname. This works perfectly with my first LEFT JOIN

  LEFT JOIN people ON inbox.newUserID=people.peopleID  



but I do not know how I can creat/filter people.firstname and people.lastname to be assigned to my third left join

  LEFT JOIN application AS applicationperson ON people.peopleID=applicationperson.peopleID  



my sql statement look like this

  SELECT inbox.inboxID, inbox.newUserID, inbox.applicationID, inbox.inboxDate, people.peopleID, people.firstname, people.lastname, people.salutationID, application.applicationID, application.peopleID

FROM inbox

LEFT JOIN people ON inbox.newUserID=people.peopleID
LEFT JOIN application ON inbox.appilicationID=application.applicationID
LEFT JOIN application AS applicationperson ON people.peopleID=applicationperson.peopleID  
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Jason ByrnesWebAssist

I'm sure i understand what you are trying to accomplish.

you want to filter the recordset to return records where the people.firstname and people.lastname have a specific value?


if so, that is not done through a join, that is done using the where clause:

SELECT inbox.inboxID, inbox.newUserID, inbox.applicationID, inbox.inboxDate, people.peopleID, people.firstname, people.lastname, people.salutationID, application.applicationID, application.peopleID

FROM inbox

LEFT JOIN people ON inbox.newUserID=people.peopleID
LEFT JOIN application ON inbox.appilicationID=application.applicationID

WHERE people.firstname = "john" AND people.lastname = "doe"

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Jenny I

Hi Jason,

The issue is that the two tables I have in my sql both have people.peopleID as foriegn keys.

so if I try to create both joins e.g.

LEFT JOIN people ON inbox.newUserID=people.peopleID
LEFT JOIN application ON people.peopleID=applicationperson.peopleID

people.firstname and people.lastname can only refer to the first join. Is there any way I maybe using the AS operator I can create some like

people.firstname AS applicationpeople.firstname so that I can have to unique values. So

applicationpeople.firstname will be related to

LEFT JOIN application ON people.peopleID=applicationperson.peopleID

and people.firstname will be related to

LEFT JOIN people ON inbox.newUserID=people.peopleID

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Jason ByrnesWebAssist

i think your thinking of this incorrectly.

people.firstname refers to the firstname column of the people table.

this has nothing to do with the first or second or third join.

it will always ever refer to the firstname column of the people table.


there is no reason to join the application table twice in the sql.

if you have a column in both the people and application table that is named the same, you can refer to them using the table.column syntax:
people.firstname - would return the firstname column from the people table

application.firstname - would return the first name column from the application table.

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Jenny I

Hi Jason

I think my problem is similar to this and believe the solution is similar. My application table does not have firstname and lastname fields. It has a peopleID foreign key which gets the data from the people table.

showthread.php?t=18122&highlight=joins

I tried the solution by changing my join to

SELECT inbox.inboxID, inbox.newUserID, inbox.applicationID, inbox.inboxDate, people.peopleID, people.firstname, people.lastname, people.salutationID, application.applicationID, application.peopleID

FROM inbox

LEFT JOIN people ON inbox.newUserID=people.peopleID
LEFT JOIN application ON inbox.appilicationID=application.applicationID
LEFT JOIN people AS applicationperson ON application.peopleID=applicationperson.peopleID

then i created these variables

<?php echo $row_WADAinbox['applicationperson.firstname']; ?>

<?php echo $row_WADAinbox['appilcationperson.lastname']; ?>

but it didnt work

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Jason ByrnesWebAssist

your select clause does not include the applicationperson.firstname and appilcationperson.lastname columns

change:
SELECT inbox.inboxID, inbox.newUserID, inbox.applicationID, inbox.inboxDate, people.peopleID, people.firstname, people.lastname, people.salutationID, application.applicationID, application.peopleID

to:
SELECT inbox.inboxID, inbox.newUserID, inbox.applicationID, inbox.inboxDate, people.peopleID, people.firstname, people.lastname, people.salutationID, application.applicationID, application.peopleID, applicationperson.firstname, appilcationperson.lastname

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Jenny I

Hi Jason

Strangely when I run the query

SELECT inbox.inboxID, inbox.newUserID, inbox.applicationID, inbox.inboxDate, people.peopleID, people.firstname, people.lastname, people.salutationID, application.applicationID, application.peopleID, applicationperson.firstname, appilcationperson.lastname

the application.fisrtname and application.lastame shows in the query however people.firstname and people.lastname dissapears. If I remove the

LEFT JOIN people AS applicationperson ON application.peopleID=applicationperson.peopleID

then people.firstname and people.lastname appears in the sequel query again. I am not quite sure why this is happening.

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Jason ByrnesWebAssist

please send a SQL dump of your tables and the full SQL so i can troubleshoot the problem using your data.

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