Improve UNION to support parenthesized SELECT and ORDER BY to close (#2417)

Implemented SQL-99 compliant solution with 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.

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: mathiasrw <[email protected]>
Co-authored-by: Mathias Wulff <[email protected]>

Author: Copilot

.gitattributes

@@ -12,6 +12,6 @@ yarn.lock binary
 # paths that don't start with / are relative to the .gitattributes folder
 #relative/path/*.txt text eol=lf
 
-src/alasqlparser.js merge=union
+src/alasqlparser.js binary
 
 

.github/copilot-instructions.md

@@ -7,54 +7,33 @@ AlaSQL is an open source SQL database for JavaScript with a focus on query speed
 ## When Implementing Features
 
 1. **Understand the issue thoroughly** - Read related test cases and existing code
-2. **Write a test first** - Create `test/test###.js` for the issue where `###` is the id of the issue we are actually fixing. 
+2. **Write a test first** - Copy test/test000.js into a new file called `test/test###.js` where where `###` is the id of the issue we are trying to solve
 3. **Verify test fails** - Run `yarn test` to confirm the test catches the issue
 4. **Implement the fix** - Modify appropriate file(s) in `src/`
-5. **Format code** - Run `yarn format` before committing
-6. **Verify test passes** - Run `yarn test` again
+  - If you modify the grammar in `src/alasqlgrammar.jison`, run `yarn jison && yarn test` to regenerate the parser and verify
+5. **Reconsider elegance** - Make sure to assess the solution and reconsider if this can be more elegant or efficient
+6. **Format code** - Run `yarn format` before committing
 
 
-## How to to test files
-1. Make a test file
-  - Name new test files as `test/test###.js` where `###` is the GitHub issue number of the issue we are actually fixing.
-    - If the file already exists we name the file test/test###-B.js
-1. Copy the structure in `test/test000.js` as a template
-3. Tests should be self-contained and clear about what they're testing
-4. Use the Mocha test framework with standard assertions
-
-## SQL Parser Modifications
-
-If a problem demands modifying the lexical parser then seek to do chances as small as possible to `src/alasqlparser.jison`. Afterwards run `yarn jison && yarn test` to confirm the result. 
-
 ## Commands
 
 ```bash
 # Install dependencies
 yarn
 
+# Generate grammar (if needed)
+yarn jison
+
 # Run tests
 yarn test
 
 # Format code
 yarn format
-
-# Build project
-yarn build
+```
 
 
 ## Files to Avoid Modifying
 - `dist/` - Generated files, will be overwritten on build
 - `src/alasqlparser.js` - Generated from Jison grammar (modify the `.jison` file instead)
 - `.min.js` files - Generated during build
 
-
-now commit the code.
-
-## When Reviewing Code
-
-- Verify tests exist for any new functionality and any regression the code changes could have affected. 
-
-## Resources
-
-- [AlaSQL Documentation](https://github.com/alasql/alasql/wiki)
-- [Issue Tracker](https://github.com/AlaSQL/alasql/issues)

test/test000.js

@@ -3,24 +3,22 @@ if (typeof exports === 'object') {
 	var alasql = require('..');
 }
 
-describe('Test 000 - multiple statements', function () {
-	const test = '000'; // insert test file number
+let testId = '000'; // Use the ID of the issue being fixed by this PR
 
+describe(`Test ${testId} - multiple statements`, function () {
 	before(function () {
-		alasql('create database test' + test);
-		alasql('use test' + test);
+		alasql('create database test' + testId);
+		alasql('use test' + testId);
 	});
 
 	after(function () {
-		alasql('drop database test' + test);
+		alasql('drop database test' + testId);
 	});
 
-	// NOTE: Tests should use assert.deepEqual to verify the complete expected output
-	// against the actual result object. This ensures comprehensive validation and
-	// makes test failures more informative by showing the full diff.
+	// NOTE: Always assert.deepEqual the final and complete output of the last call to alasql
 
 	it('A) From single lines', function () {
-		var res = [];
+		let res = [];
 		res.push(alasql('create table one (a int)'));
 		res.push(alasql('insert into one values (1),(2),(3),(4),(5)'));
 		res.push(alasql('select * from one'));
@@ -29,16 +27,16 @@ describe('Test 000 - multiple statements', function () {
 
 	it('B) Multiple statements in one string', function () {
 		//
-		var sql = 'create table two (a int);';
+		let sql = 'create table two (a int);';
 		sql += 'insert into two values (1),(2),(3),(4),(5);';
 		sql += 'select * from two;';
-		var res = alasql(sql);
+		let res = alasql(sql);
 		assert.deepStrictEqual(res, [1, 5, [{a: 1}, {a: 2}, {a: 3}, {a: 4}, {a: 5}]]);
 	});
 
 	it('C) Multiple statements in one string with callback', function (done) {
-		// Please note that first parameter (here `done`) must be called if defined - and is needed when testing async code
-		var sql = 'create table three (a int);';
+		// use first param (here `done`) when operating with async function or async code
+		let sql = 'create table three (a int);';
 		sql += 'insert into three values (1),(2),(3),(4),(5);';
 		sql += 'select * from three;';
 		alasql(sql, function (res) {