Question: Is SQLite an in-memory database?

Answer

SQLite does support in-memory databases, but it's not exclusively an in-memory database. SQLite is a software library that provides a relational database management system (RDBMS). The defining feature of SQLite is that it's serverless and zero-configuration, meaning it's very lightweight and easy to use for simple applications.

How to use SQLite as an in-memory database? Here's a Python example:

import sqlite3

# Connect to the in-memory SQLite database
conn = sqlite3.connect(':memory:')

# Create a cursor object
c = conn.cursor()

# Create a table
c.execute('''CREATE TABLE stocks
             (date text, trans text, symbol text, qty real, price real)''')

# Insert a row of data
c.execute("INSERT INTO stocks VALUES ('2006-01-05','BUY','RHAT',100,35.14)")

# Save (commit) the changes
conn.commit()

# We can also close the connection if we are done with it.
# Just be sure any changes have been committed or they will be lost.
conn.close()

In this code, sqlite3.connect(':memory:') creates a new database in RAM. From here, you can interact with your in-memory SQLite database like a regular disk-based SQLite database.

However, remember all the data stored in an in-memory database will be lost when the connection to the database is closed, hence its usage is typically limited to cases where persistence is not required, such as caching, temporary data transformations, or for testing purposes.

Also, SQLite in-memory databases can improve performance because reading and writing data directly from/to RAM is faster than reading/writing from/to disk storage.