[antlr-interest] Very weird SQL parser failures - look-ahead?

[anatoli_krassavine]

  Hello,

I tried to use Oracle 7 SQL grammar in anger. It works great for very 
complex SQL statements, but I suddenly stumbled on an unexpected 
issues with what I consider to be a very simple SQL. Could someone 
please advice.

The following statement fails with 
Exception in thread "main" line 10:2: expecting CLOSE_PAREN, 
found 'null'

------------
SELECT *
FROM
    c.abcd
WHERE
    cr.no IN 
(
SELECT cr.no FROM c.cr cr
union
SELECT a FROM abc where a=b
)
------------
On the other hand this works fine (note that "where a=b" was removed)

SELECT *
FROM
    c.abcd
WHERE
    cr.no IN 
(
SELECT cr.no FROM c.cr cr
union
SELECT a FROM abc
)
------------

AFAICC, it is not a problem with syntax, but a problem with a look-
ahead, but I do not understand how to fix this.

Any help or pointing in the right direction will be greatly 
appreciated.

Details:
Oracle 7 SQL grammar from  /grammar/ORACLE-7-SQL
No changes, conventional lexer/parser generated




 
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