{
  "nbformat": 4,
  "nbformat_minor": 5,
  "cells": [
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "# Aliases and formula columns\n",
        "\n",
        "Give a relationship path a short name, calculate each row's amount and see it change when the quantity changes.\n",
        "\n",
        "[Watch lesson 4](https://asqueel.org/learn/04-keys-and-constraints/)\n",
        "\n",
        "**Run the cells from top to bottom in a fresh Python kernel.** Each notebook includes its own starting state. SQLite runs in memory; restarting the kernel discards the database. To repeat the exercise, restart the kernel and run all cells. Colab execution requires a Google account.\n",
        "\n",
        "\u00a9 2026 Softwell S.r.l. \u00b7 Apache-2.0"
      ],
      "id": "l4-c0-b4482bdaa2f7"
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "## Before the examples: `_ = ...` is optional\n",
        "\n",
        "It assigns a return value we do not need, preventing its automatic display in the Python console or notebook. The call still runs normally. This is a Python convention, not an Asqueel requirement. When you need the result, use a meaningful variable name."
      ],
      "id": "l4-c1-5261ce0eb0bf"
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "## Prepare the notebook\n",
        "\n",
        "The video starts in a terminal. Here, install the same official package in the notebook kernel. No virtual environment or separate Python console is needed in Colab."
      ],
      "id": "l4-c2-a53efa980848"
    },
    {
      "cell_type": "code",
      "metadata": {},
      "source": [
        "%pip install -q \"asqueel[migration]==0.6.0\""
      ],
      "id": "l4-c3-5283bc5543e7",
      "execution_count": null,
      "outputs": []
    },
    {
      "cell_type": "code",
      "metadata": {},
      "source": [
        "%config InteractiveShell.ast_node_interactivity = \"all\""
      ],
      "id": "l4-c4-7a5eb4f63b61",
      "execution_count": null,
      "outputs": []
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "## Recreate the starting point\n",
        "\n",
        "The previous lessons are rebuilt below. The four fictional CSV files are included in this notebook and written into a new temporary folder. No downloads or existing database are needed."
      ],
      "id": "l4-c5-26bce07fb451"
    },
    {
      "cell_type": "code",
      "metadata": {
        "jupyter": {
          "source_hidden": true
        },
        "cellView": "form"
      },
      "source": [
        "#@title Prepare the sample CSV files\n",
        "from pathlib import Path\n",
        "import os\n",
        "import tempfile\n",
        "_lesson_folder = tempfile.TemporaryDirectory(prefix=\"asqueel-notebook-\")\n",
        "os.chdir(_lesson_folder.name)\n",
        "_csv_files = {'customers.csv': 'id,name,city\\n1,Ada,Florence\\n2,Grace,London\\n3,Linus,Helsinki\\n4,Guido,Amsterdam\\n5,Elena,Florence\\n6,Alan,Manchester\\n7,Margaret,New York\\n8,Barbara,Boston\\n', 'invoice_rows.csv': 'id,invoice_id,product_code,quantity,unit_price,total\\n1,101,TEA,2,3.50,7.00\\n2,101,COF,1,6.90,6.90\\n3,101,MUG,4,5.25,21.00\\n4,102,BTEA,2,3.20,6.40\\n5,102,HTEA,3,4.10,12.30\\n6,102,HON,4,7.50,30.00\\n7,103,SUG,3,2.30,6.90\\n8,103,CHO,4,3.90,15.60\\n9,103,BIS,1,2.80,2.80\\n10,104,JAM,4,4.60,18.40\\n11,104,OAT,1,2.40,2.40\\n12,104,JUI,2,2.70,5.40\\n13,105,WAT,1,0.90,0.90\\n14,105,LEM,2,1.80,3.60\\n15,105,KET,3,32.90,98.70\\n16,106,POT,2,18.50,37.00\\n17,106,PLT,3,6.40,19.20\\n18,106,BWL,4,7.80,31.20\\n19,107,SPO,3,9.50,28.50\\n20,107,TRY,4,14.90,59.60\\n21,107,JAR,1,8.20,8.20\\n22,108,NAP,4,12.00,48.00\\n23,108,TWL,1,5.60,5.60\\n24,108,FLT,2,2.10,4.20\\n25,109,TIN,1,6.70,6.70\\n26,109,MAT,2,11.40,22.80\\n27,109,CAF,3,29.90,89.70\\n28,110,BOT,2,13.50,27.00\\n29,110,STR,3,4.80,14.40\\n30,110,SCL,4,24.90,99.60\\n31,111,TEA,3,3.50,10.50\\n32,111,COF,4,6.90,27.60\\n33,111,MUG,1,5.25,5.25\\n34,112,BTEA,4,3.20,12.80\\n35,112,HTEA,1,4.10,4.10\\n36,112,HON,2,7.50,15.00\\n', 'invoices.csv': 'id,number,customer_id,invoice_date\\n101,INV-001,1,2026-09-28\\n102,INV-002,2,2026-09-29\\n103,INV-003,3,2026-09-30\\n104,INV-004,4,2026-10-01\\n105,INV-005,5,2026-10-02\\n106,INV-006,6,2026-10-03\\n107,INV-007,7,2026-10-04\\n108,INV-008,8,2026-10-05\\n109,INV-009,1,2026-10-06\\n110,INV-010,2,2026-10-07\\n111,INV-011,5,2026-10-08\\n112,INV-012,3,2026-10-09\\n', 'products.csv': 'code,name,category,stock\\nBTEA,Black tea,Drinks,30\\nHTEA,Herbal tea,Drinks,18\\nHON,Honey,Food,22\\nSUG,Cane sugar,Food,40\\nCHO,Dark chocolate,Food,35\\nBIS,Biscuits,Food,28\\nJAM,Strawberry jam,Food,16\\nOAT,Oat drink,Drinks,32\\nJUI,Apple juice,Drinks,26\\nWAT,Mineral water,Drinks,60\\nLEM,Lemonade,Drinks,30\\nKET,Kettle,Kitchen,9\\nPOT,Teapot,Kitchen,14\\nPLT,Plate,Kitchen,36\\nBWL,Bowl,Kitchen,24\\nSPO,Spoon set,Kitchen,20\\nTRY,Serving tray,Kitchen,11\\nJAR,Storage jar,Kitchen,25\\nNAP,Cotton napkins,Kitchen,18\\nTWL,Tea towel,Kitchen,30\\nFLT,Coffee filters,Kitchen,45\\nTIN,Tea tin,Kitchen,15\\nMAT,Table mats,Kitchen,16\\nCAF,Coffee maker,Kitchen,7\\nBOT,Water bottle,Kitchen,21\\nSTR,Tea strainer,Kitchen,23\\nSCL,Kitchen scale,Kitchen,8\\n'}\n",
        "for _name, _text in _csv_files.items():\n",
        "    _ = Path(_name).write_text(_text, encoding=\"utf-8\")\n"
      ],
      "id": "l4-c6-89efb228754e",
      "execution_count": null,
      "outputs": []
    },
    {
      "cell_type": "code",
      "metadata": {
        "jupyter": {
          "source_hidden": true
        },
        "cellView": "form"
      },
      "source": [
        "#@title Recreate the previous lessons\n",
        "\n",
        "######## Import our two tools ########\n",
        "\n",
        "from asqueel import AsqueelDb, SqlDatabaseConfig\n",
        "\n",
        "\n",
        "######## Choose SQLite in memory ########\n",
        "\n",
        "model = SqlDatabaseConfig()\n",
        "root = model.source.db(implementation=\"sqlite\")\n",
        "_ = root.connection(name=\":memory:\", implementation=\"sqlite\")\n",
        "\n",
        "\n",
        "######## Describe a product table ########\n",
        "\n",
        "shop = root.packages().package(\"shop\", sqlschema=\"shop\")\n",
        "product = shop.table(\"product\", pkey=\"code\")\n",
        "_ = product.column(\"code\", size=\":10\")\n",
        "_ = product.column(\"name\", size=\":60\")\n",
        "\n",
        "\n",
        "######## Create that table ########\n",
        "\n",
        "db = AsqueelDb(model)\n",
        "print(db.migrate().commands)\n",
        "\n",
        "\n",
        "######## Add our first product ########\n",
        "\n",
        "products = db.table(\"shop.product\")\n",
        "products.insert({\"code\": \"TEA\", \"name\": \"Tea\"})\n",
        "db.commit()\n",
        "\n",
        "\n",
        "######## Read our product ########\n",
        "\n",
        "products.query(columns=\"$code, $name\").fetch()\n",
        "\n",
        "\n",
        "######## Change its name ########\n",
        "\n",
        "products.update({\"name\": \"Green tea\"}, pkey=\"TEA\")\n",
        "db.commit()\n",
        "\n",
        "\n",
        "######## Check the update ########\n",
        "\n",
        "products.query(columns=\"$code, $name\").fetch()\n",
        "db.commit()\n",
        "\n",
        "\n",
        "######## Track category and stock ########\n",
        "\n",
        "_ = product.column(\"category\", size=\":30\")\n",
        "_ = product.column(\"stock\", dtype=\"I\")\n",
        "\n",
        "\n",
        "######## Load the updated model ########\n",
        "\n",
        "db.reloadModel(model)\n",
        "\n",
        "\n",
        "######## Add those database columns ########\n",
        "\n",
        "print(db.migrate().commands)\n",
        "\n",
        "\n",
        "######## Check our original row ########\n",
        "\n",
        "products = db.table(\"shop.product\")\n",
        "products.query(columns=\"$name, $stock\").fetch()\n",
        "db.commit()\n",
        "\n",
        "\n",
        "######## Give tea its stock ########\n",
        "\n",
        "products.update({\"category\": \"Drinks\", \"stock\": 8}, pkey=\"TEA\")\n",
        "db.commit()\n",
        "\n",
        "\n",
        "######## Read the new values ########\n",
        "\n",
        "products.query(columns=\"$name, $category, $stock\").fetch()\n",
        "db.commit()\n",
        "\n",
        "\n",
        "######## Add products from CSV ########\n",
        "\n",
        "from io import StringIO\n",
        "data = StringIO(\n",
        "    \"code,name,category,stock\\n\"\n",
        "    \"COF,Coffee,Drinks,24\\n\"\n",
        "    \"MUG,Mug,Kitchen,12\\n\"\n",
        ")\n",
        "\n",
        "\n",
        "######## Import those rows ########\n",
        "\n",
        "products.sql_insert(data, format=\"csv\")\n",
        "db.commit()\n",
        "\n",
        "\n",
        "######## List just the drinks ########\n",
        "\n",
        "products.query(\n",
        "    columns=\"$name, $stock\",\n",
        "    where=\"$category = :category\", category=\"Drinks\",\n",
        "    order_by=\"$stock DESC\",\n",
        ").fetch()\n",
        "db.commit()\n",
        "\n",
        "# Continue with lesson two.\n",
        "\n",
        "######## Check our starting point ########\n",
        "\n",
        "products.query(columns=\"$code, $name\").fetch()\n",
        "db.commit()\n",
        "\n",
        "\n",
        "######## Describe our customers ########\n",
        "\n",
        "customer = shop.table(\"customer\", pkey=\"id\")\n",
        "_ = customer.column(\"id\", dtype=\"I\")\n",
        "_ = customer.column(\"name\", size=\":60\")\n",
        "_ = customer.column(\"city\", size=\":60\")\n",
        "\n",
        "\n",
        "######## Create the customer table ########\n",
        "\n",
        "db.reloadModel(model)\n",
        "print(db.migrate().commands)\n",
        "\n",
        "\n",
        "######## Describe a dated invoice ########\n",
        "\n",
        "invoice = shop.table(\"invoice\", pkey=\"id\")\n",
        "_ = invoice.column(\"id\", dtype=\"I\")\n",
        "_ = invoice.column(\"number\", size=\":20\")\n",
        "_ = invoice.column(\"invoice_date\", dtype=\"D\")\n",
        "\n",
        "\n",
        "######## Connect invoices to customers ########\n",
        "\n",
        "customer_id = invoice.column(\"customer_id\", dtype=\"I\")\n",
        "_ = customer_id.relation(\n",
        "    \"shop.customer.id\", foreign_key=True, relation_name=\"invoices\",\n",
        ")\n",
        "\n",
        "\n",
        "######## Describe an invoice row ########\n",
        "\n",
        "invoice_row = shop.table(\"invoice_row\", pkey=\"id\")\n",
        "_ = invoice_row.column(\"id\", dtype=\"I\")\n",
        "_ = invoice_row.column(\"quantity\", dtype=\"I\")\n",
        "_ = invoice_row.column(\"unit_price\", dtype=\"N\", size=\"12,2\")\n",
        "_ = invoice_row.column(\"total\", dtype=\"N\", size=\"12,2\")\n",
        "\n",
        "\n",
        "######## Connect the row at both ends ########\n",
        "\n",
        "invoice_id = invoice_row.column(\"invoice_id\", dtype=\"I\")\n",
        "_ = invoice_id.relation(\n",
        "    \"shop.invoice.id\", foreign_key=True, relation_name=\"rows\",\n",
        ")\n",
        "product_code = invoice_row.column(\"product_code\", size=\":10\")\n",
        "_ = product_code.relation(\n",
        "    \"shop.product.code\", foreign_key=True, relation_name=\"rows\",\n",
        ")\n",
        "\n",
        "\n",
        "######## Apply the new model ########\n",
        "\n",
        "db.reloadModel(model)\n",
        "print(db.migrate().commands)\n",
        "\n",
        "\n",
        "######## Get fresh table handles ########\n",
        "\n",
        "products = db.table(\"shop.product\")\n",
        "customers = db.table(\"shop.customer\")\n",
        "invoices = db.table(\"shop.invoice\")\n",
        "rows = db.table(\"shop.invoice_row\")\n",
        "\n",
        "\n",
        "######## Inspect the row file ########\n",
        "\n",
        "from pathlib import Path\n",
        "print(\"\\n\".join(Path(\"invoice_rows.csv\").read_text().splitlines()[:4]))\n",
        "\n",
        "\n",
        "######## Expand the product catalogue ########\n",
        "\n",
        "with open(\"products.csv\", newline=\"\", encoding=\"utf-8\") as source:\n",
        "    products.sql_insert(source)\n",
        "\n",
        "db.commit()\n",
        "\n",
        "\n",
        "######## Count the catalogue ########\n",
        "\n",
        "products.query().count()\n",
        "db.commit()\n",
        "\n",
        "\n",
        "######## Import customers and their cities ########\n",
        "\n",
        "with open(\"customers.csv\", newline=\"\", encoding=\"utf-8\") as source:\n",
        "    customers.sql_insert(source)\n",
        "\n",
        "db.commit()\n",
        "customers.query(columns=\"$name, $city\", limit=3).fetch()\n",
        "db.commit()\n",
        "\n",
        "\n",
        "######## Import the invoices ########\n",
        "\n",
        "with open(\"invoices.csv\", newline=\"\", encoding=\"utf-8\") as source:\n",
        "    invoices.sql_insert(source)\n",
        "\n",
        "db.commit()\n",
        "\n",
        "\n",
        "######## Import the invoice rows ########\n",
        "\n",
        "with open(\"invoice_rows.csv\", newline=\"\", encoding=\"utf-8\") as source:\n",
        "    rows.sql_insert(source)\n",
        "\n",
        "db.commit()\n",
        "\n",
        "\n",
        "######## Check how much we imported ########\n",
        "\n",
        "invoices.query().count()\n",
        "rows.query().count()\n",
        "db.commit()\n",
        "\n",
        "\n",
        "######## Read invoices with their customers ########\n",
        "\n",
        "invoices.query(\n",
        "    columns=\"$number, $invoice_date, \"\n",
        "            \"@customer_id.name, @customer_id.city\",\n",
        "    limit=3,\n",
        ").fetch()\n",
        "db.commit()\n",
        "\n",
        "\n",
        "######## Inspect the first invoice ########\n",
        "\n",
        "rows.query(\n",
        "    columns=\"@product_code.name, \"\n",
        "            \"$quantity, $unit_price, $total\",\n",
        "    where=\"$invoice_id = :invoice\", invoice=101,\n",
        ").fetch()\n",
        "db.commit()\n",
        "\n",
        "\n",
        "######## Read across both connections ########\n",
        "\n",
        "rows.query(\n",
        "    columns=\"@invoice_id.number, \"\n",
        "            \"@invoice_id.@customer_id.city, \"\n",
        "            \"@product_code.name, $total\",\n",
        "    limit=3,\n",
        ").fetch()\n",
        "db.commit()\n",
        "\n",
        "# Continue with lesson three.\n",
        "\n",
        "######## Find invoices for Florence ########\n",
        "\n",
        "invoices.query(\n",
        "    columns=\"$number\",\n",
        "    where=\"@customer_id.city = :city\", city=\"Florence\",\n",
        ").fetch()\n",
        "\n",
        "\n",
        "######## Sort invoices by city ########\n",
        "\n",
        "invoices.query(\n",
        "    columns=\"$number, @customer_id.city\",\n",
        "    order_by=\"@customer_id.city\", limit=4,\n",
        ").fetch()\n",
        "\n",
        "\n",
        "######## Show the newest rows first ########\n",
        "\n",
        "rows.query(\n",
        "    columns=\"@invoice_id.invoice_date, $total\",\n",
        "    order_by=\"@invoice_id.invoice_date DESC\", limit=3,\n",
        ").fetch()\n",
        "\n",
        "\n",
        "######## Find rows for Florence ########\n",
        "\n",
        "rows.query(\n",
        "    columns=\"@product_code.name, $quantity\",\n",
        "    where=\"@invoice_id.@customer_id.city = :city\",\n",
        "    city=\"Florence\", limit=3,\n",
        ").fetch()\n",
        "\n",
        "\n",
        "######## Combine the conditions ########\n",
        "\n",
        "from datetime import date\n",
        "rows.query(\n",
        "    columns=\"@product_code.name, $total\",\n",
        "    where=\"@invoice_id.@customer_id.city = :city \"\n",
        "          \"AND @invoice_id.invoice_date >= :since\",\n",
        "    city=\"Florence\", since=date(2026, 10, 1),\n",
        "    order_by=\"@invoice_id.invoice_date DESC\", limit=4,\n",
        ").fetch()\n",
        "\n",
        "\n",
        "######## Close this read transaction ########\n",
        "\n",
        "db.commit()\n"
      ],
      "id": "l4-c7-0c30c6823748",
      "execution_count": null,
      "outputs": []
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "## 1 \u2014 What we'll learn in this lesson"
      ],
      "id": "l4-c8-0faae73bfca2"
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Welcome back! Here's what we'll learn in this lesson. Give a relationship path a short name, calculate each invoice row's amount, and watch that formula respond to a quantity change. One row at a time, in our existing database."
      ],
      "id": "l4-c9-d1a0ff47f37c"
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "```text\n",
        "What we'll learn in this lesson\n",
        "aliasColumn \u2192 a short name for a path\n",
        "formulaColumn \u2192 quantity times price\n",
        "Change quantity \u2192 read the new amount\n",
        "\n",
        "Same SQLite database in memory\n",
        "```"
      ],
      "id": "l4-c10-be9eb728923b"
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "## 2 \u2014 Give the city path a short name"
      ],
      "id": "l4-c11-f5cf95e6b819"
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Let's call this path city. Alias column gives our two-hop customer city a reusable name. Reload the model and get a fresh table handle."
      ],
      "id": "l4-c12-93db25938640"
    },
    {
      "cell_type": "code",
      "metadata": {},
      "source": [
        "######## Call this path city ########\n",
        "\n",
        "_ = invoice_row.aliasColumn(\n",
        "    \"city\", relation_path=\"@invoice_id.@customer_id.city\",\n",
        ")\n",
        "db.reloadModel(model)\n",
        "rows = db.table(\"shop.invoice_row\")"
      ],
      "id": "l4-c13-0a38160ef4fd",
      "execution_count": null,
      "outputs": []
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Let's read and filter with that name. Dollar city follows the original relationship path. It does not store another copy of the city."
      ],
      "id": "l4-c14-cf8367a78d87"
    },
    {
      "cell_type": "code",
      "metadata": {},
      "source": [
        "######## Read and filter with that name ########\n",
        "\n",
        "rows.query(\n",
        "    columns=\"$city, @product_code.name\",\n",
        "    where=\"$city = :city\", city=\"Florence\", limit=3,\n",
        ").fetch()\n",
        "db.commit()"
      ],
      "id": "l4-c15-5f380b58bf6b",
      "execution_count": null,
      "outputs": []
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "## 3 \u2014 Calculate the amount of each row"
      ],
      "id": "l4-c16-0324ca734518"
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Let's calculate quantity times price. Formula column declares an SQL expression. Round it to two decimal places, and describe the result as numeric."
      ],
      "id": "l4-c17-81115e44def8"
    },
    {
      "cell_type": "code",
      "metadata": {},
      "source": [
        "######## Calculate quantity times price ########\n",
        "\n",
        "_ = invoice_row.formulaColumn(\n",
        "    \"calculated_total\",\n",
        "    sql_formula=\"ROUND($quantity * $unit_price, 2)\",\n",
        "    dtype=\"N\",\n",
        ")\n",
        "db.reloadModel(model)\n",
        "rows = db.table(\"shop.invoice_row\")"
      ],
      "id": "l4-c18-0e7b101bd626",
      "execution_count": null,
      "outputs": []
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Let's read the calculated amounts. Two teas at three fifty make seven. The database evaluates the formula when we query it."
      ],
      "id": "l4-c19-1b45d6264fb4"
    },
    {
      "cell_type": "code",
      "metadata": {},
      "source": [
        "######## Read the calculated amounts ########\n",
        "\n",
        "rows.query(\n",
        "    columns=\"$quantity, $unit_price, $calculated_total\",\n",
        "    where=\"$invoice_id = :invoice\", invoice=101,\n",
        "    order_by=\"$id\",\n",
        ").fetch()\n",
        "db.commit()"
      ],
      "id": "l4-c20-55cbdec1a21f",
      "execution_count": null,
      "outputs": []
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "## 4 \u2014 No new stored columns"
      ],
      "id": "l4-c21-5492f1d07bae"
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Let's check whether the database needs changing. True means no migration is needed. Aliases and formulas add no physical columns."
      ],
      "id": "l4-c22-0978b8a34f4f"
    },
    {
      "cell_type": "code",
      "metadata": {},
      "source": [
        "######## Check whether the database needs changing ########\n",
        "\n",
        "db.migration_plan().empty"
      ],
      "id": "l4-c23-672929cd4803",
      "execution_count": null,
      "outputs": []
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "## 5 \u2014 Watch the formula respond to a change"
      ],
      "id": "l4-c24-49441651a9a8"
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Let's temporarily change the quantity to three. The calculated amount becomes ten fifty immediately. The old total imported from CSV stays seven because it is an ordinary stored column."
      ],
      "id": "l4-c25-7c1efe00e74d"
    },
    {
      "cell_type": "code",
      "metadata": {},
      "source": [
        "######## Temporarily change the quantity to three ########\n",
        "\n",
        "rows.update({\"quantity\": 3}, pkey=1)\n",
        "rows.query(\n",
        "    columns=\"$quantity, $total, $calculated_total\",\n",
        "    where=\"$id = :id\", id=1,\n",
        ").fetch()"
      ],
      "id": "l4-c26-82efcb9250d8",
      "execution_count": null,
      "outputs": []
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Let's undo that change. Rollback restores the original quantity, so the rest of our examples use the same dataset."
      ],
      "id": "l4-c27-b4973b03fdbe"
    },
    {
      "cell_type": "code",
      "metadata": {},
      "source": [
        "######## Undo that change ########\n",
        "\n",
        "db.rollback()"
      ],
      "id": "l4-c28-bc2065ac943d",
      "execution_count": null,
      "outputs": []
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "## 6 \u2014 Thank you \u2014 next steps"
      ],
      "id": "l4-c29-3ff01fa8debf"
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Thanks for following along! We named a path and calculated a row amount without storing another column. Next, we will summarize related records: invoice, customer and product totals."
      ],
      "id": "l4-c30-16292cf73296"
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "```text\n",
        "Thank you!\n",
        "aliasColumn \u2192 reuse a relationship path\n",
        "formulaColumn \u2192 calculate the row amount\n",
        "No stored column \u2192 no migration\n",
        "\n",
        "Next: aggregate related records\n",
        "```"
      ],
      "id": "l4-c31-0ab6548b03ac"
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "## Check your result\n",
        "\n",
        "Run this final cell to check the exercise."
      ],
      "id": "l4-c32-062cfb81c9cc"
    },
    {
      "cell_type": "code",
      "metadata": {},
      "source": [
        "from decimal import Decimal\n",
        "from math import isclose\n",
        "assert rows.query().count() == 36\n",
        "\n",
        "assert rows.query(where=\"$city = :city\", city=\"Florence\").count() == 12\n",
        "amounts = rows.query(columns=\"$quantity, $unit_price, $calculated_total\").fetch()\n",
        "assert all(Decimal(str(r[\"calculated_total\"])).quantize(Decimal(\".01\")) == (r[\"quantity\"] * r[\"unit_price\"]).quantize(Decimal(\".01\")) for r in amounts)\n",
        "assert rows.query(columns=\"$quantity, $total, $calculated_total\", where=\"$id = :id\", id=1).fetch()[0][\"quantity\"] == 2\n",
        "db.commit()\n",
        "assert db.migration_plan().empty\n",
        "db.commit()\n",
        "print(\"Lesson checks passed.\")\n"
      ],
      "id": "l4-c33-1cf6d02f5727",
      "execution_count": null,
      "outputs": []
    }
  ],
  "metadata": {
    "kernelspec": {
      "name": "python3",
      "display_name": "Python 3",
      "language": "python"
    },
    "language_info": {
      "name": "python"
    },
    "asqueel": {
      "version": "0.6.0",
      "lesson": 4
    }
  }
}