Re: Idea: Avoid JOINs by using path expressions to follow FKs

On Tue, Mar 30, 2021, at 21:02, Isaac Morland wrote:
> On Tue, 30 Mar 2021 at 14:30, Joel Jacobson <joel(at)compiler(dot)org> wrote:
>
>> __
>> If the expression ends with a column_name,
>> you get the value for the column.
>>
>> If the expression ends with a constraint_name,
>> you get the referenced table as a record.
>
> Can’t you just leave off the “ends with a column_name” part? If you want one of its columns, just put .column_name:
>
> table -> constraint -> ... -> constraint . column_name
>
> Then you know that -> expects a constraint_name and only that to its right.

+1

Of course! Much simpler. Thanks.

>
> Also, should the join be a left join, which would therefore return a NULL when there is no matching record? Or could we have a variation such as ->? to give a left join (NULL when no matching record) with -> using an inner join (record is not included in result when no matching record).

Interesting idea, but I think we can keep it simple, and still support the case you mention:

If we only have -> and you want to exclude records where the column is NULL (i.e. INNER JOIN),
I think we should just use the WHERE clause and filter on such condition.

>
> For the record I would find something like this quite useful. I constantly find myself joining in code lookup tables and the like, and while from a mathematical view it’s just another join, explicitly listing the table in the FROM clause of a large query does not assist with readability to say the least.

Thanks for the encouraging words. I have exactly the same experience myself and share your view.

I look forward to continued discussion on this matter.

/Joel