>> 
>> 
>> 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.

Look at a simple path expression like 

$x//a//b

(bread and butter for any semi-structured query language)

This would translate into the equivalent SQL with:
1. nested queries
2. nested RECURSIVE queries in fact
3. two outer joins.

Good luck with trying to:
1. write that by hand and
2. find a SQL implementation that optimizes and executes that properly….


And that’s “just” a simple $x//a//b…….

Now imagine your typical XQuery (soon to be JSOniq:-) program.

Best regards
Dana




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