Which programming language is typically used in AJAX transactions to query databases?

The correct answer is SQL. In AJAX (Asynchronous JavaScript and XML) transactions, SQL is the language typically used to interact with databases. When an AJAX call is made from the client-side JavaScript, it often requests data from a server-side script, which in turn uses SQL to query a database. SQL is specifically designed for managing and manipulating relational databases, making it the ideal choice for querying, inserting, updating, and deleting records in a database.

While JavaScript plays a crucial role in initiating AJAX requests and handling responses, it does not perform the actual database queries. Instead, it interacts with server-side technologies that execute SQL commands. On the other hand, PHP can be used in conjunction with SQL to handle server-side logic and database operations, but it is SQL itself that directly queries the database. HTML is a markup language for structuring content on the web and is not used for database transactions.