Implement SQL-99 compliant parenthesized SELECT support for UNION with ORDER BY

[Copilot]

Implements SQL-99 compliant support for using ORDER BY with UNION operations by adding parenthesized SELECT statement support.

Issue

The parser was throwing a syntax error when ORDER BY was used before UNION:

SELECT country, COUNT(*) AS competitors
FROM foreignCompetitors
GROUP BY country
ORDER BY country
UNION
SELECT "Total: " AS country, COUNT(*) AS competitors
FROM foreignCompetitors;

Error: Parse error on line 6: ...Y countryORDER BY UNIONSELECT "Total: ---------------------^ ... got 'UNION'

Solution

According to SQL-99 standard, ORDER BY before UNION requires the SELECT statement to be wrapped in parentheses. The fix implements proper parenthesized SELECT support:

(SELECT country, COUNT(*) AS competitors
FROM foreignCompetitors
GROUP BY country
ORDER BY country)
UNION
SELECT "Total: " AS country, COUNT(*) AS competitors
FROM foreignCompetitors;

Changes Made

• Added ParenthesizedSelect grammar rule: New rule LPAR Select RPAR allows any SELECT statement to be wrapped in parentheses, including those with ORDER BY and LIMIT clauses
• Updated UnionClause: Modified to accept both SelectWithoutOrderOrLimit (for standard queries) and ParenthesizedSelect (for queries with ORDER BY/LIMIT before UNION), supporting all set operations: UNION, UNION ALL, EXCEPT, INTERSECT, and their CORRESPONDING variants
• Updated Select rule: Added alternative production that allows starting with ParenthesizedSelect followed by UnionClause OrderClause LimitClause, enabling proper chaining
• Regenerated src/alasqlparser.js: Rebuilt the parser from the updated jison grammar file
• Created test/test2414.js: Comprehensive tests with 16 test cases verifying SQL-99 compliant syntax works correctly

Supported Syntax (SQL-99 Compliant)

1. (SELECT ... ORDER BY ...) UNION SELECT ... - Parenthesized first SELECT with ORDER BY
2. (SELECT ... ORDER BY ...) UNION (SELECT ... ORDER BY ...) - Both SELECTs parenthesized
3. SELECT ... UNION ... ORDER BY ... - Standard syntax, ORDER BY applies to entire result
4. Complex nested combinations with multiple UNIONs

Testing

• ✅ All 16 test cases in test2414.js pass, covering:
  • Parenthesized SELECT with ORDER BY/LIMIT before UNION/EXCEPT/INTERSECT
  • Both SELECTs parenthesized with ORDER BY+LIMIT
  • Standard UNION with ORDER BY at end (without parentheses)
  • Complex nested parenthesized UNIONs
  • ORDER BY with multiple columns and expressions
  • LIMIT with OFFSET
• ✅ All existing UNION tests (test017.js, test671.js) still pass
• ✅ No security vulnerabilities detected
• ✅ No breaking changes to existing functionality

The implementation is minimal, focused, and fully compliant with the SQL-99 standard for set operations with ORDER BY clauses.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>UNION with ORDER BY doesn't seem to work as expected</issue_title>
<issue_description>If I do

SELECT country, COUNT(*) AS competitors
FROM foreignCompetitors
GROUP BY country
ORDER BY country
UNION
SELECT "Total: " AS country, COUNT(*) AS competitors
FROM foreignCompetitors;

I get error: Parse error on line 6: ...Y countryORDER BY UNIONSELECT "Total: ---------------------^ Expecting 'LITERAL', 'BRALITERAL', 'LPAR', 'NUMBER', 'STRING', 'SHARP', 'DOLLAR', 'AT', 'VALUE', 'COLON', 'NOT', 'IF', 'PLUS', 'STAR', 'QUESTION', 'INSERTED', 'FIRST', 'LAST', 'DELETED', 'CURRENT_TIMESTAMP', 'CURRENT_DATE', 'JAVASCRIPT', 'NEW', 'CAST', 'CONVERT', 'SUM', 'TOTAL', 'COUNT', 'MIN', 'MAX', 'AVG', 'AGGR', 'ARRAY', 'REPLACE', 'DATEADD', 'DATEDIFF', 'TIMESTAMPDIFF', 'INTERVAL', 'TRUE', 'FALSE', 'NSTRING', 'NULL', 'EXISTS', 'ARRAYLBRA', 'BRAQUESTION', 'CASE', 'TILDA', 'MINUS', 'ATLBRA', 'LCUR', got 'UNION'

If I remove the ORDER BY clause it works.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes UNION with ORDER BY doesn't seem to work as expected #2414

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[mathiasrw]

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[mathiasrw]

@copilot Continue...

[Copilot]

Continue

I've completed the fix for the UNION with ORDER BY issue. The parse error has been resolved by modifying the grammar to allow ORDER BY clauses before UNION statements. All tests are passing. (commit: 1830831)

@copilot Continue...

Done! The fix is complete. The grammar now accepts ORDER BY before UNION, resolving the parse error from the issue. (commit: 1830831)

[mathiasrw]

Turns out this is not SQL-99 compliant. SELECT ... ORDER BY ... UNION ... is not supported. and SELECT ... UNION ... ORDER BY ... should order all of the results.

We will have to make it so we can wrap the selects in () and then we konw they belong.

so we must make it

(SELECT ... ORDER BY ...) UNION ...

and

`(SELECT ... ORDER BY ...) UNION (... ORDER BY) ... ORDER BY ...`

In the last example it does not really make sense as the order is set twice, but the notation should be supported.

@copilot

[mathiasrw]

@copilot

[Copilot]

Turns out this is not SQL-99 compliant. SELECT ... ORDER BY ... UNION ... is not supported. and SELECT ... UNION ... ORDER BY ... should order all of the results.

...

Implemented SQL-99 compliant solution. Now supports parenthesized SELECT statements: (SELECT ... ORDER BY ...) UNION ... and (SELECT ... ORDER BY ...) UNION (SELECT ... ORDER BY ...). The grammar now properly requires parentheses for ORDER BY before UNION, while still supporting standard SELECT ... UNION ... ORDER BY ... syntax. All 16 test cases pass. (commit: 26b9bfc)

@copilot

Done! The grammar now supports SQL-99 compliant parenthesized SELECT statements with ORDER BY before UNION. Tests cover all the cases you mentioned including (SELECT ... ORDER BY ...) UNION ... and complex nested scenarios. (commit: 26b9bfc)