
Understanding PromQL
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Understanding PromQL
An introduction to the PromQL query language
PromQL is one of the core features of Prometheus, allowing for powerful analysis and processing of time series.
Although QL is in the name, it is not related to SQL. Relational algebra doesn't work too well for typical calculations on multidimensional time series. Syntax wise, PromQL is closest to expressions in the C family of languages.
This course looks at each of the components of PromQL in turn, building up to real life use cases. This course is targeted towards Prometheus 2.0, though most of the material will also apply to older versions.
Table of Contents
1. Using this Training Environment
2. PromQL Theory: Selectors
 Types of Expressions
 Vector vs Range Vector
 Selectors
 Selector Safety
 Instant Vector Staleness
 Range Vectors
 Time from when?
 Exercise: Use Selectors
3. PromQL Theory: Functions
 Functions
 Math Functions
 Clamping
 Timestamps
 Time and Dates
 Gauge Range Vectors
 Counter Range Vectors
 Aggregating Across Time
 Subqueries
 Histograms
 Switching Types
 Altering Labels
 Sorting
 Missing values
 Other Functions
 Quiz
4. Aggregators and Operators
 Aggregators
 Choosing Output Labels
 Operators
 Arithmetic
 Simple Binary Operator Matching
 Matching Your Time Series
 Many to One
 Comparison Operators
 Bool vs Filtering
 Logical/Set Operators
 Quiz
5. PromQL in Practice
 From Theory to Practice
 Common Query Patterns in PromQL
 Pitfalls When Aggregating
 Machine Role Labels
 Threshold from a Metric
 Combining Alert Conditions
 Finding Big Metrics
6. Accessing PromQL
 Accessing PromQL
 HTTP API
 Query Range Computational Model
 Getting Data Aligned to a Day
 Recording Rules
 When to use rules?
 Rule Naming
 Using Rules
 Rule AntiPatterns
Prerequisites
We also recommend taking the [Prometheus Data Model](www.academy.sysdig.com) course before this one.
Credits
This course is based on one developed by Robust Perception and is used with their permission. If you want to learn more about Prometheus and PromQL, you may wish to refer to Prometheus: Up & Running by Brian Brazil of Robust Perception.