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Add UNNEST function to close #2141 (#2342)
Co-authored-by: copilot-swe-agent[bot] <[email protected]> Co-authored-by: mathiasrw <[email protected]>
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‎src/84from.js‎

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@@ -97,6 +97,35 @@ alasql.from.RANGE = function (start, finish, cb, idx, query) {
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return res;
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};
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/**
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* UNNEST function - converts an array into a table for use in FROM clauses
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*
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* This function enables flattening of nested arrays when used with CROSS APPLY or OUTER APPLY.
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*
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* @param {Array} arr - The array to unnest
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* @param {Object} opts - Options (reserved for future use)
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* @param {Function} cb - Callback function
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* @param {number} idx - Index
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* @param {Object} query - Query object
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* @returns {Array} The input array, or empty array if input is not an array
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*
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* @example
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* // Flatten nested arrays
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* SELECT b.name, e.id, e.value
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* FROM data AS b
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* CROSS APPLY (SELECT * FROM UNNEST(b.entries)) AS e
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*/
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alasql.from.UNNEST = function (arr, opts, cb, idx, query) {
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var res = arr;
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if (!Array.isArray(res)) {
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res = [];
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}
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if (cb) {
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res = cb(res, idx, query);
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}
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return res;
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};
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// Read data from any file
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alasql.from.FILE = function (filename, opts, cb, idx, query) {
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var fname;

‎test/test2141.js‎

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if (typeof exports === 'object') {
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var assert = require('assert');
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var alasql = require('..');
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} else {
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__dirname = '.';
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}
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/*
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* Test for UNNEST function to flatten nested arrays in objects
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*
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* This addresses the issue of "broadcasting" nested objects without SEARCH.
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* Using CROSS APPLY with UNNEST allows flattening of nested array properties.
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*
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* Example from the issue:
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* Input: [{ name: "a", entries: [{ id: 1, value: 2 }, { id: 3, value: 4 }] }]
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* Output: [{ name: "a", id: 1, value: 2 }, { name: "a", id: 3, value: 4 }]
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*
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* Usage:
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* SELECT parent.field, child.field
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* FROM table AS parent
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* CROSS APPLY (SELECT * FROM UNNEST(parent.array_field)) AS child
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*/
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describe('Test 2141 - UNNEST function for flattening nested objects', function () {
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it('1. Basic UNNEST function with simple array', function (done) {
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var data = [1, 2, 3, 4, 5];
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// Note: SELECT COLUMN _ is used for primitive values to return the array itself
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// rather than wrapping each value in an object
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var res = alasql('SELECT COLUMN _ FROM UNNEST(?)', [data]);
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assert.deepEqual(res, [1, 2, 3, 4, 5]);
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done();
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});
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it('2. UNNEST function with array of objects', function (done) {
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var data = [
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{id: 1, value: 2},
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{id: 3, value: 4},
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];
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var res = alasql('SELECT * FROM UNNEST(?)', [data]);
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assert.deepEqual(res, [
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{id: 1, value: 2},
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{id: 3, value: 4},
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]);
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done();
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});
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it('3. CROSS APPLY with UNNEST for nested object flattening', function (done) {
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var data = [
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{
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name: 'a',
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entries: [
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{id: 1, value: 2},
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{id: 3, value: 4},
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],
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},
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{
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name: 'b',
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entries: [
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{id: 5, value: 6},
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{id: 7, value: 8},
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{id: 9, value: 10},
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],
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},
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];
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var res = alasql(
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'SELECT b.name, e.id, e.value \
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FROM ? AS b \
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CROSS APPLY (SELECT * FROM UNNEST(b.entries)) AS e',
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[data]
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);
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assert.deepEqual(res, [
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{name: 'a', id: 1, value: 2},
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{name: 'a', id: 3, value: 4},
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{name: 'b', id: 5, value: 6},
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{name: 'b', id: 7, value: 8},
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{name: 'b', id: 9, value: 10},
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]);
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done();
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});
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it('4. OUTER APPLY with UNNEST handles empty arrays', function (done) {
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var data = [
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{
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name: 'a',
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entries: [
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{id: 1, value: 2},
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{id: 3, value: 4},
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],
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},
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{
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name: 'b',
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entries: [],
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},
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{
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name: 'c',
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entries: [{id: 5, value: 6}],
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},
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];
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var res = alasql(
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'SELECT b.name, e.id, e.value \
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FROM ? AS b \
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OUTER APPLY (SELECT * FROM UNNEST(b.entries)) AS e',
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[data]
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);
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assert.deepEqual(res, [
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{name: 'a', id: 1, value: 2},
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{name: 'a', id: 3, value: 4},
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{name: 'b', id: undefined, value: undefined},
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{name: 'c', id: 5, value: 6},
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]);
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done();
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});
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it('5. CROSS APPLY with UNNEST - join flattened data with another table', function (done) {
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var data = [
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{
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name: 'a',
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entries: [
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{id: 1, value: 2},
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{id: 3, value: 4},
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],
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},
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{
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name: 'b',
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entries: [
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{id: 1, value: 6},
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{id: 2, value: 8},
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],
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},
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];
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var lookup = [
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{id: 1, label: 'first'},
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{id: 2, label: 'second'},
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{id: 3, label: 'third'},
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];
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var res = alasql(
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'SELECT b.name, e.id, e.value, l.label \
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FROM ? AS b \
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CROSS APPLY (SELECT * FROM UNNEST(b.entries)) AS e \
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JOIN ? AS l ON l.id = e.id',
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[data, lookup]
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);
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assert.deepEqual(res, [
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{name: 'a', id: 1, value: 2, label: 'first'},
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{name: 'a', id: 3, value: 4, label: 'third'},
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{name: 'b', id: 1, value: 6, label: 'first'},
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{name: 'b', id: 2, value: 8, label: 'second'},
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]);
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done();
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});
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it('6. Flattening from database.table format', function (done) {
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alasql('CREATE DATABASE IF NOT EXISTS testdb2141');
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alasql('USE testdb2141');
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alasql('CREATE TABLE IF NOT EXISTS testtable (name STRING, entries)');
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var data = [
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{
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name: 'a',
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entries: [
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{id: 1, value: 2},
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{id: 3, value: 4},
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],
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},
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{
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name: 'b',
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entries: [
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{id: 5, value: 6},
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{id: 7, value: 8},
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{id: 9, value: 10},
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],
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},
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];
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alasql('INSERT INTO testtable SELECT * FROM ?', [data]);
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var res = alasql(
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'SELECT b.name, e.id, e.value \
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FROM testdb2141.testtable AS b \
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CROSS APPLY (SELECT * FROM UNNEST(b.entries)) AS e'
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);
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assert.deepEqual(res, [
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{name: 'a', id: 1, value: 2},
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{name: 'a', id: 3, value: 4},
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{name: 'b', id: 5, value: 6},
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{name: 'b', id: 7, value: 8},
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{name: 'b', id: 9, value: 10},
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]);
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alasql('DROP DATABASE testdb2141');
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done();
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});
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it('7. Using arrow operator for nested property access in SELECT', function (done) {
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var data = [
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{
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name: 'a',
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entries: [
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{id: 1, value: 2},
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{id: 3, value: 4},
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],
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},
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{
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name: 'b',
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entries: [{id: 5, value: 6}],
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},
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];
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var res = alasql(
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'SELECT b.name, e.id AS id, e.value AS val \
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FROM ? AS b \
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CROSS APPLY (SELECT * FROM UNNEST(b.entries)) AS e',
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[data]
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);
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assert.deepEqual(res, [
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{name: 'a', id: 1, val: 2},
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{name: 'a', id: 3, val: 4},
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{name: 'b', id: 5, val: 6},
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]);
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done();
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});
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it('8. Example from issue - exact scenario', function (done) {
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// Create database and table as in the issue
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alasql('CREATE DATABASE IF NOT EXISTS A');
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alasql('USE A');
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alasql('CREATE TABLE IF NOT EXISTS B (name STRING, entries)');
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var data = [
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{
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name: 'a',
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entries: [
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{id: 1, value: 2},
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{id: 3, value: 4},
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],
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},
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{
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name: 'b',
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entries: [
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{id: 5, value: 6},
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{id: 7, value: 8},
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{id: 9, value: 10},
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],
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},
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];
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alasql('INSERT INTO B SELECT * FROM ?', [data]);
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// Use the flattening query as suggested in the issue comments
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var res = alasql(
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'SELECT b.name, e.id, e.value \
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FROM A.B AS b \
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CROSS APPLY (SELECT * FROM UNNEST(b.entries)) AS e'
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);
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assert.deepEqual(res, [
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{name: 'a', id: 1, value: 2},
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{name: 'a', id: 3, value: 4},
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{name: 'b', id: 5, value: 6},
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{name: 'b', id: 7, value: 8},
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{name: 'b', id: 9, value: 10},
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]);
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alasql('DROP DATABASE A');
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done();
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});
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});

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