Why Do SQL Databases Require Multiple Connections for Queries?

The reason behind needing multiple connections boils down to concurrency. If only one caller is executing queries, a single connection might suffice. However, for systems that handle multiple simultaneous requests, one global connection won't work as it would serialize operations, blocking other requests. Creating a new connection for each request is inefficient, but implementing a database connection pool is a smart solution to manage multiple requests efficiently.

When you query a database, you're essentially dealing with two components: the database context and the underlying connection. Each time you establish a new context, it might seem like you're opening a new connection, but many database providers utilize connection pooling behind the scenes. If you're managing connections manually, it's crucial to implement pooling to avoid slow connections. If you’re using an ORM, it may handle pooling for you, which is the preferred way to manage connections.

Connections maintain state relevant to your requests. For simple queries, that state might not be critical, but for operations like updates or inserts, it's crucial. This is because multiple threads could be trying to modify the database simultaneously. Starting a transaction for updates ensures the database state remains consistent while you make changes. If there’s a conflict due to another connection altering the same data, your commit might fail, which is why maintaining separate connections is necessary.