isql

Isql is a command-line tool that provides an interactive SQL prompt for connecting to and managing relational database systems. The term is used for several related utilities, most notably the isql program bundled with Sybase Adaptive Server Enterprise (ASE) and its compatible clients, as well as variants used with Microsoft SQL Server and open-source projects such as FreeTDS. These tools share a common goal: give users a simple interface to issue SQL statements, run scripts, and work with query results from a terminal or shell.

Typical functionality includes establishing a connection to a database server, entering and executing SQL commands, and displaying results in a tabular format. Isql supports interactive use, script execution from files, and batch processing, often with options to specify the server, database, and authentication details. Implementations generally rely on database client libraries or protocols such as DB-Library or TDS, and they may offer features like input/output redirection, command-line options for connection parameters, and basic scripting capabilities.

The landscape of isql tools varies by vendor and platform. While still in use in some legacy environments, isql has largely been complemented or replaced for many tasks by more modern clients and interfaces, such as sqlcmd for Microsoft SQL Server or other vendor-specific utilities. Nevertheless, isql remains a recognizable name for a class of simple, text-based SQL clients used to interact with relational databases from command line environments.