docs.sheetjs.com/docz/docs/03-demos/27-local/02-websql.md

title	sidebar_label	pagination_prev	pagination_next	sidebar_custom_props
Sheets with WebSQL	Web SQL Database	demos/data/index	demos/cloud/index	summary Reading and writing data in an in-browser SQL database

import CodeBlock from '@theme/CodeBlock';

:::danger pass

WebSQL is no longer supported in Chrome or Safari.

For SQL in the browser, there are a few alternatives:

• SQL.js is a compiled version of SQLite
• AlaSQL is a pure-JS SQL engine backed by IndexedDB

:::

WebSQL (formally "Web SQL Database") was a popular SQL-based in-browser database available in Chromium and Safari. In practice, it was powered by SQLite. Many SQLite-compatible queries were supported by WebSQL engines.

:::note Historical Context

Google and Apple developed and supported WebSQL. Legacy browser vendors fought against standardization and ultimately broke the web by forcing the deprecation of the storied API.

Leveraging new technologies, many websites ship with an in-browser SQL database.

:::

The public demo https://sheetjs.com/sql generates a database from workbook.

:::info pass

WebSQL is not commonly available on server-side platforms. Typically scripts will directly query SQLite databases using connector modules.

The "SQLite" demo covers NodeJS and other platforms.

:::

Overview

Environments that support WebSQL expose the openDatabase global method. It takes 4 arguments:

• internal database name
• version string (1.0)
• public display name
• database size (measured in bytes)

The following command attempts to connect to the database named sheetql. If the database does not exist, it will create a new database with a hint to allocate 2MB of space.

const db = openDatabase('sheetql', '1.0', 'SheetJS WebSQL Test', 2097152);

Transactions and Queries

Queries are performed within transactions.

Database#transaction passes a transaction object to the callback argument:

db.transaction(function(tx) {
  /* tx is a transaction object */
});

Within a transaction, queries are performed with Transaction#executeSql. The method takes 4 arguments:

• SQL statement stored in a string
• Array of parameterized query arguments
• Success callback
• Error callback

If the query succeeds, the success callback will be invoked with two arguments:

• Transaction object
• Result of the query

If the query fails, the error callback will be invoked with two arguments:

• Transaction object
• Error information

The Web SQL Database API is callback-based. The following snippet runs one query and wraps the execution in a promise that resolves to the query result or rejects with the error:

function execute_simple_query(db, query) {
  return new Promise((resolve, reject) => {
    db.transaction(tx =>
      tx.executeSQL(query, [],
        (tx, data) => resolve(data),
        (tx, err) => reject(err)
      )
    );
  });
}

Importing Data

Importing data from spreadsheets is straightforward using the generate_sql helper function from "Generating Tables"

const stmts = generate_sql(ws, wsname);

// NOTE: tx.executeSql and db.transaction use callbacks. This wraps in Promises
for(var stmt of stmts) await new Promise((res, rej) => {
  db.transaction(tx =>
    tx.executeSql(stmt, [],
      (tx, data) => res(data), // if the query is successful, return the data
      (tx, err) => rej(err) // if the query fails, reject with the error
  ));
});

Typically worksheet objects are extracted from workbook objects¹ generated from the SheetJS read or readFile methods².

Exporting Data

The result of a SQL SELECT statement is a SQLResultSet. The rows property is a SQLResultSetRowList. It is an "array-like" structure that has length and properties like 0, 1, etc. However, this is not a real Array object!

A real Array can be created using Array.from. The SheetJS json_to_sheet method³ can generate a worksheet object⁴ from the real array:

db.readTransaction(tx =>
  tx.executeSQL("SELECT * FROM DatabaseTable", [], (tx, data) => {
    // data.rows is "array-like", so `Array.from` can make it a real array
    const aoo = Array.from(data.rows);
    const ws = XLSX.utils.json_to_sheet(aoo);
    // ... perform an export here OR wrap in a Promise
  })
);

Using book_new and book_append_sheet⁵, a workbook object can be created. This workbook is typically exported to the filesystem with writeFile⁶.

Live Demo

:::note Tested Deployments

This browser demo was tested in the following environments:

Browser	Date
Chrome 118	2024-06-29

Browsers that do not support WebSQL will throw errors:

Browser	Date	Error Message
Chrome 126	2024-06-29	openDatabase is not defined
Safari 17.1	2024-06-29	Web SQL is deprecated
Firefox 127	2024-06-29	openDatabase is not defined

:::

Export Demo

The following demo generates a database with 5 fixed SQL statements. Queries can be changed in the Live Editor. The WebSQL database can be inspected in the "WebSQL" section of the "Application" Tab of Developer Tools:

function SheetQL() {
  const [out, setOut] = React.useState("");
  const queries = [
    'DROP TABLE IF EXISTS Presidents',
    'CREATE TABLE Presidents (Name TEXT, Idx REAL)',
    'INSERT INTO Presidents  (Name, Idx) VALUES ("Barack Obama", 44)',
    'INSERT INTO Presidents  (Name, Idx) VALUES ("Donald Trump", 45)',
    'INSERT INTO Presidents  (Name, Idx) VALUES ("Joseph Biden", 46)'
  ];
  const xport = React.useCallback(async() => {
    /* prep database */
    const db = openDatabase('sheetql', '1.0', 'SheetJS WebSQL Test', 2097152);

    for(var q of queries) await new Promise((res, rej) => {
      db.transaction((tx) => {
        tx.executeSql(q, [], (tx, data) => res(data), (tx, err) => rej(err));
      });
    });

    /* pull data and generate rows */
    db.readTransaction(tx => {
      tx.executeSql("SELECT * FROM Presidents", [], (tx, data) => {
        const aoo = Array.from(data.rows);
        setOut("QUERY RESULT:\n" + aoo.map(r => JSON.stringify(r)).join("\n") + "\n")
        const ws = XLSX.utils.json_to_sheet(aoo);
        const wb = XLSX.utils.book_new();
        XLSX.utils.book_append_sheet(wb, ws, "Presidents");
        XLSX.writeFile(wb, "SheetQL.xlsx");
      });
    });
  });
  return ( <pre>{out}<button onClick={xport}><b>Fetch!</b></button></pre> );
}

Server-Side SQLite

The exposition has been moved to a separate page.

---

1. See "Workbook Object" ↩︎

2. See read and readFile in "Reading Files" ↩︎

3. See json_to_sheet in "Utilities" ↩︎

4. See "Sheet Objects" ↩︎

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

6. See writeFile in "Writing Files" ↩︎