Query Language

A computer language used to make queries into databases and information systems.

A query language is a specialized programming language designed for retrieving and manipulating data stored in databases or other data management systems. Query languages provide a structured way to express requests for specific data, filtering criteria, sorting orders, and aggregation operations.

SQL (Structured Query Language) is the most widely used query language, designed for relational databases like PostgreSQL, MySQL, and SQL Server. It provides commands for selecting, inserting, updating, and deleting data, as well as defining schemas and managing access. NoSQL databases use their own query mechanisms, such as MongoDB's query documents or DynamoDB's key-condition expressions.

In the API context, GraphQL functions as a query language for APIs, allowing clients to specify exactly which data fields they need. API gateways can interact with query languages in several ways: translating incoming API requests into database queries, caching query results, and enforcing query complexity limits to prevent expensive queries from overloading backend databases. Some gateways support direct database-to-API mapping, automatically generating API endpoints from database schemas.