[xquery-talk] the stupidity of using SQL as a query language for JSON

[Ihe Onwuka]

So SQL over JSON = Turing Tarpit.

Fair summarisation?

On Mon, Jun 1, 2015 at 5:28 PM, Michael Kay <mike at saxonica.com> wrote:

>
>> Well, if you’re going to apply SQL to JSON (say), then the first thing
>> you have to do is define a mapping from JSON to tables. That’s not
>> difficult to do.
>>
>> If by the “closure property” you want the result of any SQL query to be
>> the representation of some JSON structure, then you’re not going to achieve
>> that. That’s essentially the same as the update problem.
>>
>>
> So pretty much no  subqueries (ok somebody is going to say that any query
> entailing a subquery can be rewritten without one) but AFAIC  the language
> you are talking about isn't really SQL then.
>
>
> I don’t follow. You can write any query you like; it’s just that the
> result is a table that might not be mappable back to JSON.
>
>
>> So I'm SOL if it's a date then.
>
>
> You won’t get any dates in the table representation of JSON, but you can
> get them in tables returned by a query.
>
>
>
>>
>> Forgive me if I'm wrong. But I still don't believe I can write a
> statement that gets me the 5th row of the table.
>
>
> Well, a typical representation of a JSON array [“a”, “b”, “c”] might be
> the table
>
> ARRAYS
> ID       INDEX    TYPE   VALUE
> 001     0             String   “a”
> 001     1             String   “b”
> 001     2             String   “c”
>
> and the query to get item 2 of array 001 would be
>
> SELECT TYPE, VALUE FROM ARRAYS WHERE ID=001 AND INDEX=2
>
> As far as I understand it this is similar to the mapping that SQL Server
> uses for XML.
>
>
>
> How would you  predict a priori what your table and column names would be
> and how many of them.
>
>
> If you’ve got no schema then you have to use a generic mapping in which
> the table and column names are generic concepts such as ARRAY, MAP, etc.
>
>
>
>
> If you don't can't predict the schema your semi-structured is going to
> generate then  how could you write your query.
>
>
> With difficulty. I can’t see anyone wanting to write it by hand.
>
> Michael Kay
> Saxonica
>
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