Re: Recursive query syntax ambiguity

"Andrew Dunstan" <andrew@dunslane.net> writes:

> Can you post the rules you have so far that you're playing around with? (Also
> maybe the rules from the standard - I don't have a copy handy).

This is the best compromise I've come up with so far. It makes CYCLE a
reserved word and requires a CYCLE clause if there's a SEARCH clause.


Here are the grammar rules from the spec (I've attached PDFs of the syntax
pages for the two productions I'm describing since the text copy/paste comes
out pretty poorly)



7.13 <query expression>
Function
Specify a table.
Format
<query expression> ::=
[ <with clause> ] <query expression body>
<with clause> ::=
WITH [ RECURSIVE ] <with list>
<with list> ::=
<with list element> [ { <comma> <with list element> }... ]
<with list element> ::=
<query name> [ <left paren> <with column list> <right paren> ]
AS <left paren> <query expression> <right paren> [ <search or cycle clause> ]
<with column list> ::= <column name list>
<query expression body> ::=
<query term>
| <query expression body> UNION [ ALL | DISTINCT ]
[ <corresponding spec> ] <query term>
| <query expression body> EXCEPT [ ALL | DISTINCT ]
[ <corresponding spec> ] <query term>
<query term> ::=
<query primary>
| <query term> INTERSECT [ ALL | DISTINCT ]
[ <corresponding spec> ] <query primary>
<query primary> ::=
<simple table>
| <left paren> <query expression body> <right paren>
<simple table> ::=
<query specification>
| <table value constructor>
| <explicit table>
<explicit table> ::= TABLE <table or query name>
<corresponding spec> ::=
CORRESPONDING [ BY <left paren> <corresponding column list> <right paren> ]
<corresponding column list> ::= <column name list>

7.14 <search or cycle clause>
Function
Specify the generation of ordering and cycle detection information in the result of recursive query expressions.
Format
<search or cycle clause> ::=
<search clause>
| <cycle clause>
| <search clause> <cycle clause>
<search clause> ::=
SEARCH <recursive search order> SET <sequence column>
<recursive search order> ::=
DEPTH FIRST BY <sort specification list>
| BREADTH FIRST BY <sort specification list>
<sequence column> ::= <column name>
<cycle clause> ::=
CYCLE <cycle column list> SET <cycle mark column> TO <cycle mark value>
DEFAULT <non-cycle mark value> USING <path column>
<cycle column list> ::=
<cycle column> [ { <comma> <cycle column> }... ]
<cycle column> ::= <column name>
<cycle mark column> ::= <column name>
<path column> ::= <column name>
<cycle mark value> ::= <value expression>
<non-cycle mark value> ::= <value expression>





--
  Gregory Stark
  EnterpriseDB          http://www.enterprisedb.com