Expo

Documentation

SQLite

This module gives access to a database that can be queried through a WebSQL-like API. The database is persisted across restarts of your app.
An example to do list app is available that uses this module for storage.

Installation

For managed apps, you'll need to run expo install expo-sqlite. To use it in a bare React Native app, follow its installation instructions.

API

import { SQLite } from 'expo-sqlite';

SQLite.openDatabase(name, version, description, size)

Open a database, creating it if it doesn't exist, and return a Database object. On disk, the database will be created under the app's documents directory, i.e. ${Expo.FileSystem.documentDirectory}/SQLite/${name}.

Arguments

  • name (string) -- Name of the database file to open.
The version, description and size arguments are ignored, but are accepted by the function for compatibility with the WebSQL specification.

Returns

Returns a Database object, described below.

Database objects

Database objects are returned by calls to SQLite.openDatabase(). Such an object represents a connection to a database on your device. They support one method:
  • db.transaction(callback, error, success)
    Execute a database transaction.

    Parameters

    • callback (function) -- A function representing the transaction to perform. Takes a Transaction (see below) as its only parameter, on which it can add SQL statements to execute.
    • error (function) -- Called if an error occured processing this transaction. Takes a single parameter describing the error.
    • success (function) -- Called when the transaction has completed executing on the database.

Transaction objects

A Transaction object is passed in as a parameter to the callback parameter for the db.transaction() method on a Database (see above). It allows enqueuing SQL statements to perform in a database transaction. It supports one method:
  • tx.executeSql(sqlStatement, arguments, success, error)
    Enqueue a SQL statement to execute in the transaction. Authors are strongly recommended to make use of the ? placeholder feature of the method to avoid against SQL injection attacks, and to never construct SQL statements on the fly.

    Parameters

    • sqlStatement (string) -- A string containing a database query to execute expressed as SQL. The string may contain ? placeholders, with values to be substituted listed in the arguments parameter.
    • arguments (array) -- An array of values (numbers or strings) to substitute for ? placeholders in the SQL statement.
    • success (function) -- Called when the query is successfully completed during the transaction. Takes two parameters: the transaction itself, and a ResultSet object (see below) with the results of the query.
    • error (function) -- Called if an error occured executing this particular query in the transaction. Takes two parameters: the transaction itself, and the error object.

ResultSet objects

ResultSet objects are returned through second parameter of the success callback for the tx.executeSql() method on a Transaction (see above). They have the following form:
{
  insertId,
  rowsAffected,
  rows: {
    length,
    item(),
    _array,
  },
}
  • insertId (number) -- The row ID of the row that the SQL statement inserted into the database, if a row was inserted.
  • rowsAffected (number) -- The number of rows that were changed by the SQL statement.
  • rows.length (number) -- The number of rows returned by the query.
  • rows.item (function) -- rows.item(index) returns the row with the given index. If there is no such row, returns null.
  • rows.array (_number) -- The actual array of rows returned by the query. Can be used directly instead of getting rows through rows.item().

Executing statements outside of a transaction

Please note that you should use this kind of execution only when it is necessary. For instance, when code is a no-op within transactions (like eg. PRAGMA foreign_keys = ON;).
const db = SQLite.openDatabase('dbName', version);

db.exec([{ sql: 'PRAGMA foreign_keys = ON;', args: [] }], false, () =>
  console.log('Foreign keys turned on')
);