Maybe this was obvious, but I never thought I could do this kind of queries
in DAL.
Okay, let's say I have 2 tables:
Tags = db.define_table('tag', Field('name'))
Post = db.define_table('post', Field('title'), Field('tag', 'reference
tag'))
Now, doing a join is easy using the query *(db.post.tag == db.tag.id)*
But if I have the following 2 tables, where a post might have many tags:
Tags = db.define_table('tag', Field('name'))
Post = db.define_table('post', Field('title'), Field('tag', 'list:reference
tag'))
How do I select tags that occur in posts? It turns out that this can be
done very nice using the query: *db.post.tag.contains( db.tag.id )*
*
*
I have used "contains", but I had thought that the argument for it must be
a constant (e.g. a specific tag such as "news"), not something like
db.tag.id.
Nice.
Counting tags occurrence (e.g. if you want to have a tag cloud) turns out
to be quite simple: *db( db.post.tag.contains(db.tag.id)
).select(db.tag.ALL, db.tag.id.count(), groupby=db.tag.name)*
Nice!!
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