Denes, Where and how do I display db._lastsql?
The example comes from: http://mdp.cti.depaul.edu/examples/default/dal the example about Left Outer Joins I guess the idea of the example in SQL reads like: SELECT person.name, dog.name FROM person LEFT OUTER JOIN friendship ON person.id==friendship.person LEFT OUTER JOIN dog ON dog.id==friendship.dog WHERE person.id>0 In the example: query=(db.person.id>0) and: friends=(db.person.id==db.friendship.person)& (db.dog.id==db.friendship.dog) to me this is the JOIN condition of an INNER JOIN, so I have no idea why Massimo repeats it in the OUTER JOIN example. Next in the example is this line: rows=db(query).select(db.person.name,db.dog.name,left=db.dog.on (friends)) here I don't understand the left=db.dog.on(friends) part. You use a LEFT OUTER JOIN to not loose the persons that don't have dogs in the result. In the view this is indicated by 'nobody'. However, in the friends condition you already loose the persons without a dog, then, when you LEFT OUTER JOIN dog on friends that doesn't make sense. {{extend 'layout.html'}} {{for row in rows:}} {{=row.person.name}} is friend of {{=row.dog.name or nobody}} <br /> Is there a flaw in my reasoning? > What you want is probably; > rows=db(db.person.id>0).select(db.person.name,db.dog.name,left= > [db.friendship. > on(db.friendship.person==db.person.id),db.dog.on > (db.friendship.dog==db.dog.id)]) Yes, to make sure I understand this ... left=[db.friendship.on(db.friendship.person==db.person.id),db.dog.on (db.friendship.dog==db.dog.id)]) in SQL would read like: FROM friendship LEFT OUTER JOIN person ON friendship.person==person.id LEFT OUTER JOIN dog ON friendship.dog==dog.id If I am right here I am reassured. Kind regards, Annet. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "web2py Web Framework" group. To post to this group, send email to web2py@googlegroups.com To unsubscribe from this group, send email to web2py+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/web2py?hl=en -~----------~----~----~----~------~----~------~--~---
