SQL injection into form

Is it possible to inject SQL into a read_data? If so, how to do it? If not, is there a way to do this?
I would like to make an intersect query between 2 tables but I don't know how to do this.
​
Thanks

if you want to build a relation between 2 tables then you need to add a new model and select the relation type, better start trying this on the new v7 beta5 here:
http://www.chronoengine.com/blog

Adding a new model makes a join query though doesn't it Max? Is that different to intersect?

Hum ok, is it possible to simulate the intersect in php with a loop on the arrays I want to test the value of the targeted variable and store the valid results in another array to return (in total 3 arrays)?
I'm having trouble to realize the previous solution.

I think "intersect" is the join, so just add a relation and check the returned results!