[antlr-interest] Re: Again Infinite recursion on SQL table_ref <-> join_table

[Ruslan Zasukhin]

on 9/4/02 21:01, Sinan at sinan.karasu at boeing.com wrote:

>> For all, I will show here where problem happens.
>> In Standard SQL 92 we have the next rules. I have simplify them to extract
>> only important part here:
>> 
>> joined_table
>>     :    table_reference "join" table_reference
>>     ;
>> 
>> table_reference
>>     :    table_name             // IDENT
>>     |    subquery               // '(' query ')'
>>     |    joined_table
>>     ;
>> 
> 
> yacc would resolve this with precedence rules. So
> what is needed is the determination of the meaning
> 
> a join b join c.
> is it left associative? right assoc? or non.
> 
> I suspect it is non, so
> 
> joined_table
>    :    table_reference ("join"^ joined_table)?
>    ;
> 
> table_reference
>    :    table_name             // IDENT
>    |    subquery               // '(' query ')'
>    ;
> 
> 
> is probably the right approach. So
> 
> a join b join c
> 
> would become
> join
> |
> a--join
>  |
>  b--c

Okay, I see idea. But what you suggest if JOIN should be left associative?
In fact it must be left associative...

> Sinan (who likes tail recursion...)

Now I know whom I will bother!!!  :-)

-- 
Best regards,
Ruslan Zasukhin      [ I feel the need...the need for speed ]
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web: http://www.paradigmasoft.com

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