Re: SQL grammar

[Evan Lavelle]

Evan Lavelle wrote:
> Check the logs, as Hans suggests. For starters, though, what's this:
>
> NOT IN ((SELECT '*' FROM SCONST))
>
> What sort of 'search_cond' is it? First branch, second branch, or both? 
> It can't be both; that's a conflict.

Sorry, didn't read your first post; seems you already knew this.

There's no general fix. You need a detailed understanding of your 
language, and you have to formulate the grammar in a way that doesn't 
have these overlaps. There are a lot of SQL parsers on the net, so that 
would be a good place to start.

In this simple case, your problem is that a query_specification can be 
both a query and an expression. This might make sense to a human, but 
not to a parser. You appear to be trying to fix this by the use of 
brackets, but this won't work, since a bracketed expression is still an 
expression. There are various things you can try, but which one you 
should use depends on the language itself, which I know nothing about:

1 - completely subsume queries into expressions

2 - completely exclude queries from expressions

3 - allow both query_lists and expressions to include 
query_specifications, but make sure that you never write a production 
that actually uses both a query_list and an expression

Evan