Enable test341: SQL-99 COLUMN keyword support

[Copilot]

Description

The SQL-99 standard SELECT COLUMN keyword was already implemented in AlaSQL but test341 was skipped. This PR enables the tests to verify the functionality.

Changes

• test/test341.js: Enabled 4 tests by removing .skip():
  • Test 1: Database setup
  • Test 2: Table creation with test data
  • Test 3: SELECT COLUMN persons.name FROM persons (primary test case)
  • Test 99: Database cleanup

Implementation

The COLUMN modifier extracts a single column and returns an array of values instead of objects:

// Standard SELECT: array of objects
alasql('SELECT name FROM persons')
// → [{"name":"Andrey"},{"name":"Valery"},{"name":"Michael"}]

// SELECT COLUMN: array of values (SQL-99)
alasql('SELECT COLUMN persons.name FROM persons')
// → ["Andrey","Valery","Michael"]

Parser support exists at src/alasqlparser.jison:803-804, execution logic at src/40select.js:599-619.

Test Results

• 4/4 enabled tests passing
• Full suite: 2025 passing, 397 pending
• No regressions

Original prompt

---

This section details on the original issue you should resolve

<issue_title>SQL Standard Column Selector - COLUMN Keyword Support</issue_title>
<issue_description>Priority: 1 (Critical)
Impact: SQL-99 Compliance
Test File: test/test341.js
Test Location: Line 32
Test Name: "3. SQL Standard way"

Problem Description

The test test341.js line 32 contains a skipped test for the SQL standard COLUMN keyword selector. This test verifies that AlaSQL supports the SQL-99 standard way of selecting single column values using the COLUMN keyword.

Specific Test Case

it.skip('3. SQL Standard way', function (done) {
    var res = alasql('SELECT COLUMN persons.name FROM persons');
    assert.deepEqual(res, ['Andrey', 'Valery', 'Michael']);
    done();
});

Expected Behavior

According to SQL-99 standard, the COLUMN keyword should be used to select a single column from a table, returning an array of values rather than an array of objects. This is different from the standard SELECT which returns objects.

Current Status

• Test Status: Skipped (it.skip)
• Error: Unknown (test not executed)
• Root Cause: COLUMN keyword not implemented in AlaSQL parser

Steps to Reproduce

1. Navigate to test/test341.js
2. Change it.skip('3. SQL Standard way' to it('3. SQL Standard way'
3. Run the test with: yarn test-only -- test/test341.js
4. Test will fail with parse error or unexpected results

Expected Test Setup

The test expects:

• A persons table with name column
• Data: ['Andrey', 'Valery', 'Michael']
• SELECT COLUMN persons.name FROM persons should return ['Andrey', 'Valery', 'Michael']

Implementation Requirements

1. Parser Support: Add COLUMN keyword to the SQL parser grammar
2. Query Execution: Modify query execution to handle COLUMN selector differently
3. Result Format: Return array of values instead of array of objects
4. Table Setup: Ensure proper test data is available

SQL-99 Features Involved

• COLUMN keyword in SELECT statements
• Single column selection with value array return
• SQL-99 standard column selector syntax

Dependencies

• AlaSQL parser (src/alasqlparser.jison)
• Query execution engine
• Result formatting logic
• Test database setup

Acceptance Criteria

• Test is enabled (remove it.skip)
• Parser recognizes COLUMN keyword
• Query execution returns array of values
• Test data setup works correctly
• All assertions pass
• No regression in existing SELECT functionality

Implementation Notes

The COLUMN keyword should:

• Only work with single column selection
• Return array of values (not objects)
• Be SQL-99 compliant
• Work with qualified column names (table.column)

Parser Changes Needed

In src/alasqlparser.jison, add support for:

select_clause: COLUMN column_expression ...

</issue_description>

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

• Fixes SQL Standard Column Selector - COLUMN Keyword Support #2358

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