Xataface Forums

I hate to sound a pain; Can someone help explain grafted fields in a different manner than what is in the wiki:
http://xataface.com/wiki/Grafted_fields

I'm just not grasping the concept of what it achieves. If I understand correctly, it can be used to append an input screen so you can add related records also.

Sorry for the confusion and thank you for you help!

I have attached a section of an incomplete manual that explains a little bit more about grafted fields. Perhaps this will help.

Still slightly lost...

Can someone interpret the following statement in regards to grafted fields:

Code: Select all

__sql__ = "select p.*, d.total from programmation p left join dev d on p.id_programmation=d.id_programmation"

I'm confused on these parts:
p.*
d.total
p
dev d on p.id_programmation=d.id_programmation

p.* = All columns in the programmation
d.total = The total column of the dev table
p = The alias for the programmation table
dev d = Assigning the alias "d" to refer to the table "dev"
on p.id_programmation=d.id_programmation = The join clause (joining the programmation table with the dev table on the programmation_id field)

Here is my attempt at a grafted field. This fields.ini is for the GENERAL table:

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__sql__="SELECT GENERAL.*, MLS.Provider FROM GENERAL LEFT JOIN MLS ON GENERAL.BWA_ID=MLS.BWA_ID"
//

Code: Select all

//
[Provider]
order=13

However the grafted field does not show up on my New/Edit record view.

Am I doing this correctly?

Grafted fields are read-only. They won't show up on new/edit forms. They will show up in the list view, details view, and the find form.

-Steve

Thank you for letting me know. I have an appropriate question in another thread that would have been posted next so I will just put in a link to the other thread.

Thanks again,Steve!

http://xataface.com/forum/viewtopic.php?f=4&t=6674

Code: Select all

__sql__="SELECT GENERAL.*, MLS.Provider FROM GENERAL LEFT JOIN MLS ON GENERAL.BWA_ID=MLS.BWA_ID"

Can you add a where clause to this so it will only display based on the value of the field MLS.Provider?

...WHERE MLS.PROVIDER == "BWA".

Don't use where clauses in the __sql__ grafted field directive. Use security filters for that.

I'm lost again!

Can you provide me a manual page on this or an example. The link on the wiki to the man page is broken. I'm trying to bring a related field into my list view. But it needs to check that field in the related record and only display if it is a matches the case, otherwise display NULL.

Thank you and Thank you again!

A little bit on setting security filters.
http://xataface.com/dox/core/trunk/clas ... b4a1280c63

There are actually quite a few forum posts on the topic but you may have to dig a bit. There may be some stuff in the wiki too.

May I ask why a WHERE clause in a grafted field statement is inadvisable?

Also, how can I make something like a grafted field that is writeable? It's a lot easier to add information in two tables at once, particularly if they are linked by a one to one relationship.

May I ask why a WHERE clause in a grafted field statement is inadvisable?

Because when you implement a custom __sql__ query it effectively replaces any occurrences of the table name, in existing SQL queries, with a subquery defined by the __sql__. In some cases, however, it may still use just the table name. It helps if both of these cases are the same except for the addition of the extra columns. If you use a where clause then it may lead to some unexpected results.

Of course, you *can* use a where clause as long as the result of your query has a one-to-one mapping with the rows of the original table.

Most of the time, if you want to use a where clause, you are really wanting a default filter. In these cases you should either set a security filter (if it is a permissions issue), or just add a default search in the beforeHandleRequest method.

-Steve