Repository query page

[davydovanton]

We should add a new page with repository query examples.

TODO

• joins;
• groub by;
• where with block (ILIKE, IN, etc);
• order;
• some SQL functions (type casting for example);
• #exist?

If you want to see something special please, add comment with it

[malin-as]

Hi,

Based on my experience with my current project, I'd like to propose docs on (or a small snippet about the feature not being available):

• "chained associations", for instance A has_many B, B has_many C, and C has_many D
• composite primary keys (doesn't seem to work at the moment?)
• transactions
• using SELECT COUNT(*) rather than using the count method on a SELECT *