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Thread: parser problem

parser problem

From
Michael Meskes
Date:
Is it correct that the following two statements are equal?

select "a" from foo;

select a from foo;


That results in the following problem for ecpg:

When I'm in SQL mode (that is after reading "exec sql") I do not get
quotations. But what do I do with this?

exec sql whenever sqlerror do printf("There was an error\n");

Since my lex file is almost the same as scan.l I wonder if anyone has an
idea.

Michael
--
Dr. Michael Meskes, Project-Manager    | topsystem Systemhaus GmbH
meskes@topsystem.de                    | Europark A2, Adenauerstr. 20
meskes@debian.org                      | 52146 Wuerselen
Go SF49ers! Go Rhein Fire!             | Tel: (+49) 2405/4670-44
Use Debian GNU/Linux!                  | Fax: (+49) 2405/4670-10

Re: [HACKERS] parser problem

From
"Thomas G. Lockhart"
Date:
> Is it correct that the following two statements are equal?
> select "a" from foo;
> select a from foo;

Yes.

> That results in the following problem for ecpg:
> When I'm in SQL mode (that is after reading "exec sql") I do not get
> quotations. But what do I do with this?
>
> exec sql whenever sqlerror do printf("There was an error\n");
>
> Since my lex file is almost the same as scan.l I wonder if anyone has
> an idea.

What different kinds of clauses are available with the "whenever ...
do"? My Ingres manual indicates that the syntax is:

  exec sql whenever <condition> <action>

where <condition> is one of:

  sqlwarning
  sqlerror
  sqlmessage
  not found
  dbevent

and the <action> is one of:

  continue
  stop
  goto <label>
  call <procedure>

where <procedure> cannot be called with any arguments. This syntax would
be easy to parse with your existing lexer. My SQL books shows an even
more limited syntax with only "continue" and "goto" allowed.

If you want to allow some other syntax, including double-quoted strings,
then you will need to implement it explicitly in your grammar.

                       - Tom

Re: [HACKERS] parser problem

From
Michael Meskes
Date:
Thomas G. Lockhart writes:
> where <condition> is one of:
>
>   sqlwarning
>   sqlerror
>   sqlmessage
>   not found
>   dbevent

At the moment we only can sqlerror and not found.

>   continue
>   stop
>   goto <label>

Got these plus go to <label> and sqlprint.

>   call <procedure>

Hmm, this is called "do" in Oracle. I think I allow both for compatibility.

> where <procedure> cannot be called with any arguments. This syntax would
> be easy to parse with your existing lexer. My SQL books shows an even
> more limited syntax with only "continue" and "goto" allowed.

Yes, but we don't have to play it down to the standard, do we? :-)

> If you want to allow some other syntax, including double-quoted strings,
> then you will need to implement it explicitly in your grammar.

IMO an argument is a very good idea. So I have to think about it a little
bit more.

Michael
--
Dr. Michael Meskes, Project-Manager    | topsystem Systemhaus GmbH
meskes@topsystem.de                    | Europark A2, Adenauerstr. 20
meskes@debian.org                      | 52146 Wuerselen
Go SF49ers! Go Rhein Fire!             | Tel: (+49) 2405/4670-44
Use Debian GNU/Linux!                  | Fax: (+49) 2405/4670-10