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https://issues.apache.org/jira/browse/DERBY-2374?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12770400#action_12770400
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Mamta A. Satoor commented on DERBY-2374:
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I am looking at this more, but the root of the problem might be the following
piece of code in sqlgrammar.jj in FromTable tableFactor() throws
StandardException method
|
// There is a grammar ambiguity with nested parentheses here.
// A series of left parentheses could introduce either a table
// reference or a derived table. For example:
//
// (((select c from t) a inner join (select d from s) b ))
//
// and:
//
// (((select c from t) a)))
//
// To distinguish these two cases, we consider anything that starts
// with a single parenthesis and either SELECT or VALUES to be
// a derived table, and anything else to be a table reference.
// Note that we can't use the subqueryFollows() lookahead method,
// because it skips over all leading left parentheses to decide
// whether a subquery follows.
LOOKAHEAD( {
getToken(1).kind == LEFT_PAREN &&
(
getToken(2).kind == SELECT ||
getToken(2).kind == VALUES
)
} )
I will debug more but it looks like we are not differentiating correctly the
first select inside the parenthese to mean <left paren> <query expression body>
<right paren>
select c1 from ((select t1.c1 from t1) union (select t2.c1 from t2)) t1t2;
> UNION PROBLEM WITH PARENTHESIS
> ------------------------------
>
> Key: DERBY-2374
> URL: https://issues.apache.org/jira/browse/DERBY-2374
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.1.3.3, 10.2.2.0, 10.3.3.1, 10.4.2.1, 10.5.3.1,
> 10.6.0.0
> Reporter: Kenneth Gee
> Priority: Minor
>
> The following query shows the error using the Derby demo toursDB:
> SELECT FLIGHT_ID , SEGMENT_NUMBER , ARRIVE_TIME
> FROM (
> (SELECT HW.FLIGHT_ID , HW.SEGMENT_NUMBER , HW.ARRIVE_TIME FROM
> FLIGHTS HW)
> UNION
> (SELECT SW.FLIGHT_ID , SW.SEGMENT_NUMBER , SW.ARRIVE_TIME FROM
> FLIGHTS SW)
> ) SRC;
> ERROR 42X01: Syntax error: Encountered "UNION" at line 4, column 12.
> The following query works:
> SELECT FLIGHT_ID , SEGMENT_NUMBER , ARRIVE_TIME
> FROM (
> SELECT HW.FLIGHT_ID , HW.SEGMENT_NUMBER , HW.ARRIVE_TIME FROM
> FLIGHTS HW
> UNION
> SELECT SW.FLIGHT_ID , SW.SEGMENT_NUMBER , SW.ARRIVE_TIME FROM
> FLIGHTS SW
> ) SRC;
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