docs.sheetjs.com/docz/docs/03-demos/23-data/17-mariadb.md

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Sheets with MariaDB and MySQL	MariaDB / MySQL	demos/cli/index	demos/local/index	sql true

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MariaDB is an open source object-relational database system compatible with MySQL.

SheetJS is a JavaScript library for reading and writing data from spreadsheets.

This demo uses SheetJS to exchange data between spreadsheets and MariaDB databases. We'll explore how to save tables from a database to spreadsheets and how to add data from spreadsheets into a database.

:::caution pass

It is strongly recommended to use MariaDB with a query builder or ORM.

While it is possible to generate SQL statements directly, there are many subtle details and pitfalls. Battle-tested solutions generally provide mitigations against SQL injection and other vulnerabilities.

:::

:::note Tested Deployments

This demo was tested in the following environments:

MariaDB	Connector Library	Date
11.2.2	mysql2 (3.6.5)	2023-12-04

:::

Integration Details

The SheetJS NodeJS module can be loaded in NodeJS scripts that connect to MariaDB and MySQL databases.

This demo uses the mysql2 connector module¹, but the same mechanics apply to other MariaDB and MySQL libraries.

Exporting Data

Connection#execute returns a Promise that resolves to a result array. The first entry of the result is an array of objects.

The SheetJS json_to_sheet method² can generate a worksheet object³ from the array of objects:

const mysql = require("mysql2/promise"), XLSX = require("xlsx");
const conn = await mysql.createConnection({
  database: "SheetJSMariaDB",
  /* ... other options ... */
});

const table_name = "Tabeller1"; // name of table

/* fetch all data from specified table */
const [rows, fields] = await conn.execute(`SELECT * FROM ${mysql.escapeId(table_name)}`);

/* generate a SheetJS worksheet object from the data */
const worksheet = XLSX.utils.json_to_sheet(rows);

A workbook object can be built from the worksheet using utility functions⁴. The workbook can be exported using the SheetJS writeFile method⁵:

/* create a new workbook and add the worksheet */
const wb = XLSX.utils.book_new();
XLSX.utils.book_append_sheet(wb, worksheet, "Sheet1");

/* export workbook to XLSX */
XLSX.writeFile(wb, "SheetJSMariaDBExport.xlsx");

Importing Data

The SheetJS sheet_to_json function⁶ takes a worksheet object and generates an array of objects.

Queries must be manually generated from the objects. Assuming the field names in the object match the column headers, a loop can generate INSERT queries.

:::danger pass

MariaDB does not allow parameterized queries with variable column names

INSERT INTO table_name (?) VALUES (?);
-- ---------------------^ variable column names are not valid

Queries are generated manually. To help prevent SQL injection vulnerabilities, the undocumented escapeId method ⁷ escapes identifiers and fields.

:::

/* generate an array of arrays from the worksheet */
const aoo = XLSX.utils.sheet_to_json(ws);

const table_name = "Blatte1"; // name of table

/* loop through the data rows */
for(let row of aoo) {
  /* generate INSERT column names and values */
  const ent = Object.entries(row);
  const Istr = ent.map(e => I(e[0])).join(", ");
  const Vstr = ent.map(e => E(e[1])).join(", ");

  /* execute INSERT statement */
  await conn.execute(`INSERT INTO ${I(table_name)} (${Istr}) VALUES (${Vstr})`);
}

Creating a Table

The array of objects can be scanned to determine column names and types. With the names and types, a CREATE TABLE query can be written.

Implementation Details (click to show)

The aoo_to_mariadb_table function:

• scans each row object to determine column names and types
• drops and creates a new table with the determined column names and types
• loads the entire dataset into the new table

/* create table and load data given an array of objects and a mysql2 connection */
async function aoo_to_mariadb_table(conn, aoo, table_name) {
  /* define types that can be converted (e.g. boolean can be stored in float) */
  const T_FLOAT = ["DOUBLE", "BOOLEAN"];
  const T_BOOL =  ["BOOLEAN"];

  /* types is a map from column headers to Knex schema column type */
  const types = {};

  /* names is an ordered list of the column header names */
  const names = [];

  /* loop across each row object */
  aoo.forEach(row =>
    /* Object.entries returns a row of [key, value] pairs */
    Object.entries(row).forEach(([k,v]) => {

      /* If this is first occurrence, mark unknown and append header to names */
      if(!types[k]) { types[k] = ""; names.push(k); }

      /* skip null and undefined values */
      if(v == null) return;

      /* check and resolve type */
      switch(typeof v) {
        /* change type if it is empty or can be stored in a float */
        case "number": if(!types[k] || T_FLOAT.includes(types[k])) types[k] = "DOUBLE"; break;
        /* change type if it is empty or can be stored in a boolean */
        case "boolean": if(!types[k] || T_BOOL.includes(types[k])) types[k] = "BOOLEAN"; break;
        /* no other type can hold strings */
        case "string": types[k] = "TEXT"; break;
        default: types[k] = "TEXT"; break;
      }
    })
  );

  const I = (id) => mysql.escapeId(id), E = (d) => mysql.escape(d);

  /* Delete table if it exists in the DB */
  await conn.execute(`DROP TABLE IF EXISTS ${I(table_name)};`);

  /* Create table */
  {
    const Istr = Object.entries(types).map(e => `${I(e[0])} ${e[1]}`).join(", ");
    await conn.execute(`CREATE TABLE ${I(table_name)} (${Istr});`);
  }

  /* Insert each row */
  for(let row of aoo) {
    const ent = Object.entries(row);
    const Istr = ent.map(e => I(e[0])).join(", ");
    const Vstr = ent.map(e => E(e[1])).join(", ");
    await conn.execute(`INSERT INTO ${I(table_name)} (${Istr}) VALUES (${Vstr})`);
  }

  return conn;
}

Complete Example

0. Install and start the MariaDB server.

Installation Notes (click to show)

On macOS, install the mariadb formula with Homebrew:

brew install mariadb

The last few lines of the installer explain how to start the database:

Or, if you don't want/need a background service you can just run:
// highlight-next-line
  /usr/local/opt/mariadb/bin/mysqld_safe --datadir\=/usr/local/var/mysql

Run the command to start a local database instance.

1. Drop any existing database with the name SheetJSMariaDB:

mysql -e 'drop database if exists SheetJSMariaDB;'

:::info pass

If the server is running elsewhere, or if the username is different from the current user, command-line flags can override the defaults.

Option	Explanation
-h HOSTNAME	Name of the server
-P PORT	specifies the port number
-U USERNAME	specifies the username
-p PASSWORD	specifies the password

:::

2. Create an empty SheetJSMariaDB database:

mysql -e 'create database SheetJSMariaDB;'

Connector Test

3. Create a project folder:

mkdir sheetjs-mariadb
cd sheetjs-mariadb
npm init -y

4. Install the mysql2 connector module:

npm i --save mysql2@3.6.5

5. Save the following example codeblock to MariaDBTest.js:

const mysql = require("mysql2/promise");
(async() => {

const conn = await mysql.createConnection({
  database:"SheetJSMariaDB",
// highlight-start
  host: "127.0.0.1", // localhost
  port: 3306,
  user: "sheetjs",
  //password: ""
// highlight-end
});

const [rows, fields] = await conn.execute('SELECT ? as message', ['Hello world!']);
console.log(rows[0].message); // Hello world!
await conn.end();

})();

6. Edit the new MariaDBTest.js script and modify the highlighted lines from the codeblock to reflect the database deployment settings.

• Set user to the username (it is almost certainly not "sheetjs")

• If the server is not running on your computer, set host and port to the correct host name and port number.

• If the server expects a password, uncomment the password line and replace the value with the password.

7. Run the script:

node MariaDBTest.js

It should print Hello world!

:::caution pass

If the output is not Hello world! or if there is an error, please report the issue to the mysql2 connector project for further diagnosis.

:::

Add SheetJS

8. Install dependencies:

{\ npm i --save https://cdn.sheetjs.com/xlsx-${current}/xlsx-${current}.tgz}

9. Download SheetJSMariaDB.js:

curl -LO https://docs.sheetjs.com/mariadb/SheetJSMariaDB.js

This script will:

• read and parse the test file pres.numbers
• create a connection to the SheetJSMariaDB database on a local MariaDB server
• load data from the first worksheet into a table with name Presidents
• disconnect and reconnect to the database
• dump data from the table Presidents
• export the dataset to SheetJSMariaDB.xlsx

10. Edit the SheetJSMariaDB.js script.

The script defines an opts object:

const XLSX = require("xlsx");
const opts = {
  database:"SheetJSMariaDB",
// highlight-start
  host: "127.0.0.1", // localhost
  port: 3306,
  user: "sheetjs",
  //password: ""
// highlight-end
};

Modify the highlighted lines to reflect the database deployment settings.

• Set user to the username (it is almost certainly not "sheetjs")

• If the server is not running on your computer, set host and port to the correct host name and port number.

• If the server expects a password, uncomment the password line and replace the value with the password.

11. Fetch the example file pres.numbers:

curl -L -O https://docs.sheetjs.com/pres.numbers

12. Run the script:

node SheetJSMariaDB.js

13. Verify the result:

• SheetJSMariaDBExport.xlsx can be opened in a spreadsheet app or tested in the terminal

npx xlsx-cli SheetJSMariaDBExport.xlsx

• The database server can be queried using the mysql command line tool.

If the server is running locally, the command will be:

mysql -D SheetJSMariaDB -e 'SELECT * FROM `Presidents`;'

---

1. See the official mysql2 website for more info. ↩︎

2. See json_to_sheet in "Utilities" ↩︎

3. See "Sheet Objects" in "SheetJS Data Model" for more details. ↩︎

4. See "Workbook Helpers" in "Utilities" for details on book_new and book_append_sheet. ↩︎

5. See writeFile in "Writing Files" ↩︎

6. See sheet_to_json in "Utilities" ↩︎

7. The mysql2 connector library escapeId method is not mentioned in the documentation but is present in the TypeScript definitions. ↩︎