Contents

Q for Mortals

by Jeffry A. Borror

Version 4.1 November 2025

Published in HTML by Kx Systems, by permission. Please notify any errors in this edition to docs@kx.com.

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• Preface
• 0. Overview
  • 0.0 The Evolution of Q
  • 0.1 Philosophy
  • 0.2 Mathematics Refresher
• 1. Q Shock and Awe
  • 1.1 Starting q
  • 1.2 Variables
  • 1.3 Whitespace
  • 1.4 The Q Console
  • 1.5 Comments
  • 1.6 Assignment
  • 1.7 Order of Evaluation
  • 1.8 Data Types 101
  • 1.9 Lists 101
  • 1.10 Functions 101
  • 1.11 Functions on Lists 101
  • 1.12 Example: Fibonacci Numbers
  • 1.13 Example: Newton's Method for n^th Roots
  • 1.14 Example: FIFO Allocation
  • 1.15 Dictionaries and Tables 101
  • 1.16 qSQL 101
  • 1.17 Example: Trades Table
  • 1.18 File I/O 101
  • 1.19 Interprocess Communication 101
  • 1.20 Example: Asynchronous Callbacks
• 2. Basic Data Types: Atoms
  • 2.0 Overview
  • 2.1 Integer Data
  • 2.2 Floating Point Data
  • 2.3 Binary Data
  • 2.4 Text Data
  • 2.5 Temporal Data
  • 2.6 Arithmetic Infinities and Nulls
  • 2.7 Nulls
• 3. Lists
  • 3.0 Overview
  • 3.1 Introduction to Lists
  • 3.2 Simple Lists
  • 3.3 Empty and Singleton Lists
  • 3.4 Indexing
  • 3.5 Combining Lists
  • 3.6 Lists as Maps
  • 3.7 Nesting
  • 3.8 Iterated Indexing and Indexing at Depth
  • 3.9 Indexing via Lists
  • 3.10 Elided Indices
  • 3.11 Rectangular Lists and Matrices
  • 3.12 Pattern Matching on Lists (Advanced)
  • 3.13 Basic List Operators
• 4. Operators
  • 4.0 Operators Are Functions
  • 4.1 Operator Precedence
  • 4.2 Match (~)
  • 4.3 Equality and Relational Operators
  • 4.4 Basic Arithmetic: +, -, *, %
  • 4.5 Greater | and Lesser &
  • 4.6 Amend (:)
  • 4.7 Exponential Primitives: sqrt, exp, log, xexp, xlog
  • 4.8 More Numeric Primitives
  • 4.9 Operations on Temporal Values
  • 4.10 Operations on Infinities and Nulls
  • 4.11 Views (::) (Advanced)
• 5. Dictionaries
  • 5.0 Overview
  • 5.1 Dictionary Basics
  • 5.2 Operations on Dictionaries
  • 5.3 Column Dictionaries
  • 5.4 Flipping a Dictionary
• 6. Functions
  • 6.0 Overview
  • 6.1 Function Specification
  • 6.2 Call-by-Name
  • 6.3 Local and Global Variables
  • 6.4 Projection
  • 6.5 Everything Is a Map
  • 6.6 Atomic Functions
  • 6.7 Iterators
  • 6.8 General Application
  • 6.9 Composition
• 7. Transforming Data
  • 7.1 Types and Cast
  • 7.2 Cast
  • 7.3 Data to and from Text
  • 7.4 Creating Typed Empty Lists
  • 7.5 Enumerations
• 8. Tables
  • 8.0 Overview
  • 8.1 Table Definition
  • 8.2 Empty Tables and Schema
  • 8.3 Basic select and update
  • 8.4 Primary Keys and Keyed Tables
  • 8.5 Foreign Keys and Virtual Columns
  • 8.6 Link Columns
  • 8.7 Working with Tables and Keyed Tables
  • 8.8 Complex Column Data
  • 8.9 Attributes
• 9. Queries: q-sql
  • 9.0 Overview
  • 9.1 Inserting Records
  • 9.2 upsert
  • 9.3 The select Template
  • 9.4 The exec Template
  • 9.5 The update Template
  • 9.6 The delete Template
  • 9.7 Sorting
  • 9.8 Renaming and Rearranging Columns
  • 9.9 Joins
  • 9.10 Parameterized Queries
  • 9.11 Views
  • 9.12 Functional Forms
  • 9.13 Examples
• 10. Execution Control
  • 10.0 Overview
  • 10.1 Control Flow and Conditionals
  • 10.2 Debugging
  • 10.3 Scripts
  • 10.4 Pattern Matching
• 11. I/O
  • 11.0 Overview
  • 11.1 Data Files
  • 11.2 Save and Load on Tables
  • 11.3 Splayed Tables
  • 11.4 Text Data
  • 11.5 Parsing Records
  • 11.6 Compression
  • 11.7 Data At Rest Encryption (DARE)
  • 11.8 Interprocess Communication
  • 11.9 Special Handles
  • 11.10 Basic HTTP and WebSockets
  • 11.11 HTTP and JSON
  • 11.12 TLS and SSL
• 12. Workspace Organization
  • 12.0 Overview
  • 12.1 Namespaces
  • 12.2 Namespace Implementation
  • 12.3 Creating Namespaces
  • 12.4 Namespace as Dictionary
  • 12.5 Expunging from a Namespace
  • 12.6 Saving and Loading Namespace Content
  • 12.7 Working in a Namespace
• 13. Commands and System Variables
  • 13.1 Command Format
  • 13.2 Command Line Parameters
  • 13.3 System Variables
• 14. Introduction to kdb+
  • 14.0 Overview
  • 14.1 Tables in Memory and Serialization
  • 14.2 Splayed Tables
  • 14.3 Partitioned Tables
  • 14.4 Segmented Tables
  • 14.5 .Q Utilities for Splayed and Partitioned
  • 14.6 Kdb+ Database
  • 14.7 Putting It All Together
  • 14.8 There's No Place Like QHOME
• Appendix A. Built-in Functions