Android SQLite Database

Introduction

The creation of Android applications depends heavily on the Android SQLite Database, a strong and adaptable data storage solution. This integrated relational database management system, which is a component of the Android operating system, offers a simple and effective method of managing structured data inside of apps.

The widely-used, serverless, open-source, and self-contained SQLite database engine forms the foundation of the Android SQLite Database. Because of its straightforward, dependable architecture and compact size, it is the perfect option for places with limited resources, including mobile devices. SQLite eliminates the need for a separate server and allows simple local data persistence by storing data in a single file on the device's storage system.

SQLite Database in android interoperability with the SQL (Structured Query Language) standard is one of its main benefits. Using SQL statements, developers may define tables, columns, and connections between data elements. Because of the database's conformance to the SQL standard, using current SQL knowledge and abilities is simple.

Importance of Using SQLite in Android development

SQLite is an essential tool for managing data storage and durability that is used extensively in Android development. Let's examine why SQLite is essential for Android development.

• Embedded and lightweight:
  SQLite is intended to be embedded, with a tiny footprint and little resource needs. It functions as an embedded database system, which means that no additional server is required for it to run on the device itself. Because of this feature, it is a great option for mobile systems like Android where resources are frequently scarce.
• Local Data Storage:
  Android SQLite enables programmers to keep data on the device locally. Applications that must run offline or with sporadic network access depend on this functionality to function. The user experience and productivity are improved by using SQLite, which enables programs to store and retrieve vital data without needing a continual network connection.
• Structured Data Management:
  SQLite offers a structured and well-organized method of managing data. Using SQL statements, developers may define tables, columns, and relationships, ensuring data consistency and integrity. The ability to structure data makes it simpler to deal with complicated datasets and carry out advanced data operations by enabling efficient data manipulation, querying, and retrieval.
• SQL Compatibility:
  The SQLite database in Android is built on the SQL (Structured Query Language) standard. The database is compatible with SQL, allowing developers to take advantage of their current SQL knowledge and expertise. Developers may easily construct sophisticated queries and carry out a wide range of actions thanks to SQL's robust and standardized syntax for interacting with databases.
• Transaction Support:
  SQLite database in android offers transaction management, enabling programmers to combine several database operations into a single, atomic operation. All of the processes contained inside a transaction must be completed for it to be successful, or none of them must be applied. Particularly when handling concurrent operations or intricate data manipulations, this atomicity attribute aids in maintaining data integrity and consistency.
• Indexing and query optimization:
  By utilizing indexes and query optimization techniques, SQLite database in android offers effective data retrieval. Developers can speed up data retrieval processes by building indexes on frequently used columns. By choosing the most effective execution plan, the query optimizer in SQLite uses cost-based query planning and execution to guarantee optimal query performance.
• Widely Used and Battle-Tested:
  One of the most used database engines in the world, SQLite is renowned for its dependability, stability, and performance. It is a dependable option for data storage in Android applications because it has undergone considerable testing and optimization over the years. Because of its popularity, there is a sizable development community and copious documentation, which makes it simpler to locate help and resources.
• Security and Privacy:
  To protect the security and privacy of important data, SQLite database in android are always maintained in an encrypted manner. An additional degree of security against unauthorized access is provided by the fact that an SQLite database's data can only be viewed by the program that generated it.

Database - Package

The database package in Android development provides classes and interfaces for managing data storage and persistence. The main class, SQLiteOpenHelper, helps with version control and database creation. The SQLiteDatabase class enables developers to run SQL queries, manage databases, and perform operations like adding, updating, and querying data. Custom classes that extend SQLiteOpenHelper connect with the database, while the Cursor class retrieves query results. The package also includes utility classes for constructing complex SQL queries.

Database - Creation

The database package in Android development supports several useful features in addition to database creation that improves data management and manipulation within applications. Let's examine a few of these features:

• Database Upgrade:
  When the application version changes, the database package offers means for updating the database schema. The SQLiteOpenHelper subclass's onUpgrade() function allows programmers to specify how to update the database schema to suit changes in the application. As a result, the migration of data between various versions of the database schema is certain to be seamless.
• Retrieval of Data:
  The database package provides several options for getting data out of the database. The query() function of the SQLiteDatabase class allows programmers to execute SELECT queries and obtain certain data depending on criteria. The software also offers options for grouping the results, sorting them, and using sophisticated filtering rules. The query results are conveniently navigated and retrieved using the Cursor class.
• Data Insertion, Updating, and Deletion:
  The database package offers methods for inserting, updating, and deleting data to change the data in the database. The SQLiteDatabase class's insert(), update(), and delete() functions enable programmers to add new entries, edit existing ones, and delete data from tables, respectively.
• Transactions:
  Transactions are essential for preserving the consistency and integrity of data in a database. Through the beginTransaction(), setTransactionSuccess(), and endTransaction() methods of the SQLiteDatabase class, the database package offers transaction management. Multiple database operations can be included within a transaction block, which guarantees that either all of the actions are successfully carried out or none of them are applied. By doing so, atomicity is guaranteed and data corruption is prevented.
• Raw SQL Execution:
  Using the execSQL() function of the SQLiteDatabase class, the database package enables developers to execute raw SQL statements directly on the database. This helps carry out intricate database operations that may be difficult to accomplish using high-level query techniques. When employing raw SQL statements, care must be taken to avoid potential SQL injection problems.
• Database Backup and Restore:
  The database package includes tools for saving a copy of the database and restoring it if necessary. Developers can create a backup file containing the database contents using the backup() function of the SQLiteDatabase class. In contrast, using a previously produced backup file to restore the database is possible with the restore() technique. These features are helpful for synchronization, migration, and data recovery.
• Content Providers:
  The database package encourages the use of content providers, which allow applications to safely share data. The manner that content providers expose data to other applications, enforce data access restrictions and deal with data inquiries and alterations are standardized. For creating and communicating with content providers, the database package includes classes like ContentProvider and ContentResolver.

CRUD operations in SQLite

To handle data in SQLite, basic database operations known as CRUD operations, which stand for Create, Read, Update, and Delete, are utilized. Examining each of these actions in the context of SQLite databases will be helpful.

Creating a Database

In SQLite, you must establish a database schema that contains tables, columns, constraints, and indexes. By extending the SQLiteOpenHelper class and overriding the onCreate() function, this is often accomplished. You use the execSQL() function of the SQLiteDatabase class inside of this method to run SQL commands to construct tables and specify their structure. You may start performing CRUD operations on the database after it has been built.

Database - Insertion

Use the insert() function of the SQLiteDatabase class to add data to an SQLite database. The table name, column values, and optional null column hack are the inputs for this procedure. To input data, you first build a ContentValues object, which symbolizes a collection of column-value pairs. After that, to put the data into the database, you use the insert() function with the table name and ContentValues object.

Delete Information From A Database

Use the delete() function of the SQLiteDatabase class to remove data from an SQLite database. The table name, an optional WHERE clause, and optional selection arguments are all required inputs for this function. The selection parameters supply the values for the WHERE clause's placeholders, which define the criteria for removing particular rows. You can delete rows from the selected table depending on the provided requirements by using the delete() function with the proper arguments.

Update A Database

The update() function of the SQLiteDatabase class is used to update data in an SQLite database. The inputs for this method are the table name, the new column values, the WHERE clause, and any optional selection arguments. Similar to the insertion procedure, the new column values are given using a ContentValues object. The selection parameters supply the values for the placeholders in the WHERE clause, which decides which rows to update.

Database - Fetching

The query() function of the SQLiteDatabase class is used to get data from an SQLite database. Using this technique, you may run SELECT queries and get data from one or more tables. It requires as parameters the name of the table, the projection (the columns to be included in the output), the optional WHERE clause, selection arguments, the optional GROUP BY and HAVING clauses, the optional ORDER BY clause, and the optional LIMIT clause. To cycle over the result set and acquire the necessary data, use methods like moveToFirst() and getString() on the Cursor object.

To manage data in SQLite databases, CRUD operations (Create, Read, Update, and Delete) are necessary. Using SQLiteOpenHelper, you define the schema to build a database. Update() is used for updating, delete() is used for deletion, and the insert() function is used for insertion. The query() function, which produces a Cursor object to iterate through the query results, is used to retrieve data.

Database - Helper Class

The Android SQLiteOpenHelper class is a utility class that makes managing SQLite database in android easier. It offers a practical method for building, upgrading, and managing the database's lifespan. Let's get started with a description of the lifetime of the SQLiteOpenHelper class.

Typically, the SQLiteOpenHelper class is expanded by developing a subclass tailored to the requirements of your application. Your application code and the underlying SQLite database are connected via this subclass. It manages operations including database creation, version control, and giving users access to a SQLiteDatabase class instance.

Explanation of SQLiteOpenHelper class

Two crucial methods, onCreate() and onUpgrade(), must be overridden when building a subclass of SQLiteOpenHelper. These methods, which the SQLiteOpenHelper class calls at certain times in its lifecycle, let you provide unique behavior for creating and updating databases.

• onCreate():
  When a database is first built, the onCreate() function is invoked. Its duties include running SQL queries to create tables, columns, constraints, and indexes as well as other operations that construct the database structure. The relevant SQL queries for building the database structure are executed inside of this function using the execSQL() method of the SQLiteDatabase class.
• onUpgrade():
  The onUpgrade() function is invoked whenever a version update necessitates an upgrade of the database. It enables you to specify the database schema modifications that will be necessary to support application updates. By using this strategy, you may often change tables, add or remove columns, or migrate data from one schema to another. To avoid data loss or corruption, it is essential to properly manage data migration during database updates.

In addition to these two, the onOpen() function, which is available from the SQLiteOpenHelper class, is called when the database is opened. Whenever the database connection has to be opened, this function can be altered to carry out any further setup or initialization procedures that are necessary.

Understanding the SQLiteOpenHelper lifecycle

• Initialization:
  The onCreate() function of the application or as necessary creates an instance of the SQLiteOpenHelper subclass. The database name and version are entered into the constructor of the SQLiteOpenHelper class at this point.
• First-time Database Creation:
  The onCreate() function is called if the database does not already exist or if the version supplied is greater than the version of the installed database. Here, you design the database schema and run the required SQL operations to build the basic framework.
• Database Opening:
  The onOpen() method is called before returning the SQLiteDatabase instance when you use the getWritableDatabase() or getReadableDatabase() methods of the SQLiteOpenHelper class to request a writable or readable instance of the database. This enables you to carry out any startup or setup procedures particular to each database session.
• Database Upgrade:
  The onUpgrade() method is triggered if the SQLiteOpenHelper subclass specifies a database version that is greater than the one that is currently in use. This approach takes care of updating the database schema to take into account the adjustments the new version demands. Tables may need to be changed, columns may need to be changed, or data may need to be moved from the old schema to the new one.
• Normal Database Use:
  Using the provided SQLiteDatabase instance, you may carry out standard database activities including data insertion, retrieval, updating, and deletion after the database has been built or updated. Using the methods offered by the SQLiteDatabase class, these activities are often carried out within the application's code.

Example Demonstrating The Use Of Sqlite Database

Assume for the moment that we are creating a straightforward task management tool that enables users to create, view, change, and delete tasks.

• Set up the project structure and create a new Android project in Android Studio.
• Create a task model class that has attributes like the task ID, title, description, and completion status to represent tasks. The tasks will be mapped to database entries using this class.

• Create a subclass of SQLiteOpenHelper to handle database creation and upgrading. Let's name it TaskDbHelper. Override the onCreate() and onUpgrade() methods to define the database schema.

• Create a data access object (DAO) class, let's name it TaskDao, to encapsulate database operations such as insertion, retrieval, updating, and deletion of tasks.