# Prometheus
All Prometheus notes →1 — PromQL Fundamentals
The four PromQL data types, label matchers and selectors, and how to run PromQL outside the Prometheus UI via the HTTP API.
2 — PromQL Functions
Math, date/time, type-conversion, and sorting functions; the rate() vs irate() decision; and the histogram_quantile() function-call mechanics.
3 — Aggregation Operators
The PromQL aggregation operator table, the by clause, the without clause, and worked collapsing examples across single and multiple labels.
4 — Vector Matching
How PromQL matches labels between two instant vectors — ignoring/on, one-to-one vs many-to-one/one-to-many with group_left/group_right — plus arithmetic, comparison, and logical operators.
5 — Advanced PromQL
The complete recording-rule syntax reference (rule files, worked example, level:metric_name:operations naming), the offset and @ modifiers, and subqueries.