SQL grammar

[RichardT]

Hello All:

First off, I would like to apologize in case this post does not belong to
this
forum. If that is the case, please let me know if there is another forum
where I
can post my question. 

I am writing a parser to parse SQL (actually T-SQL for MS Sql Server). I am
getting a shift/reduce conflict that I don't know how to solve. I know the
reason of the conflict and I can give you 2 valid SQL statements that can be 
parsed in two diffrent ways. I just don't know how to solve that in my
grammar.

Consider the following two valid SQL statements:

Statement #1:
select b from s where b not in ( (select a from t where a = 1), 8, 9 );

Statement #2:
select b from s where b not in ( (select a from t where a = 1) 
                                       union (select a from t where a = 2)
);
                                       

In stmt#1, the search condition inside the "not in" is a list of
expressions.
In stmt#2, the search condition inside the "not in" is another query
combined
with UNION.

Here is a simplified version of my bison grammar:
=========================================================================
expression: ICONST
            | expression '+' expression
            | expression '-' expression
            | expression '*' expression
            | expression '/' expression
            | expression '%' expression
                ...
                ...
            | '(' expression ')'
            | '(' query_specification ')'
                ...
                ...
            ;

exp_list:   exp_list ',' expression
            | expression
            ;

search_condition:   expression '>' expression
                    | expression '<' expression
                    | expression LIKE expression
                        ...
                        ...
                    | expression IN '(' exp_list ')'
                    | expression NOT IN '(' exp_list ')'
                    | expression IN '(' query_list ')'
                    | expression NOT IN '(' query_list ')'
                        ...
                        ...
                    ;

query_list: query_list UNION query_list
            | '(' query_list ')'
            | query_specification
            ;

/*
 * This is the grammar for a select statement
 */
query_specification:    SELECT select_list into_clause from_clause
                        where_clause group_by_clause having_clause

=========================================================================

The ambiguity arise when I give a statement like this:

Statement #3:
select b from s where b not in ( (select a from t where a = 1) );

The parser can treat the search condition as an exp_list or a query_list.

Can someone point me out how to formulate my grammar.

Thanks
Richard




-- 
View this message in context: 
http://www.nabble.com/SQL-grammar-tp17127516p17127516.html
Sent from the Gnu - Bison - Help mailing list archive at Nabble.com.