Help Center> MapReduce Service> Developer Guide (3.x)> CQL Development Guide (Security Mode)> Overview> Common Concepts
Common Concepts
Window
Window: A way for processing unbounded and streaming events. A window sets an event stream to a static view at a moment for various query operations on database tables.
Expression
An expression is a set of symbols and operators. The CQL parsing engine processes an expression to obtain single values. A simple expression can be a constant, variable, or function. Two or more simple expressions can be combined as a complex expression by using operators.
keytab file
A key file for storing user information. Applications use the key file for API authentication on FusionInsight MRS.
Parent topic: Overview
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