# Glossary

## Database

A named server database, or a file-backed or in-memory database opened by an embedded application. A native session selects a managed database with USE.

## Connection and session

A connection owns SQL and transaction state. A native session lasts for the connection; an HTTP session lasts for one request. Temporary objects and uncommitted changes belong to that scope.

## Namespace

A connection's `main`, `temp` or attached database name. A namespace qualifies a table within a connection. It is distinct from managed server database selection.

## Statement and request

A statement is one parsed SQL operation. A request can contain several statements and has one query ID. Request limits can span all of those statements.

## Format

A named encoding that writes result rows, reads INSERT rows, or both. CoordinatorDB format names use snake_case. Each format documents its supported directions and options.

## Database setting and format setting

A database setting is stored with the database and managed by SET or its documented alternative. A format setting applies to one statement through SETTINGS and is not persisted.

## System catalog

The server's `system` relations expose database metadata, settings, functions, formats, active requests and history. Qualify them with `system.`.

## Query log and diagnostic log

The query log is structured request history available as `system.query_log`. The diagnostic log contains service messages and errors. These are separate interfaces with different fields and uses.