Advanced Query (Datalog)

Team Mut···last changed 2026-05-22

A Simple Query filters one property and becomes a view. But the moment you want to connect two things — open tasks from a quarter's meetings, grouped by project — the filter line runs out. Datalog starts exactly there: you describe the relationship as a rule, and mium derives the rest.

Where the filter line runs out

A filter line checks blocks one by one against fixed criteria. It can't join across blocks, derive nothing and add nothing up. Multi-criteria reports you'd otherwise click together by hand from several views — and maintain them the same way. Datalog turns that around: one rule that describes the relationships, and an engine that evaluates it.

Anatomy of a rule

A Datalog rule has two parts: :find says which value you want to see, :where lists the conditions — one per line. Variables such as ?task connect the lines; where the same variable appears more than once, that is a join.

[:find ?task
 :where
 [?task "type" "task"]
 [?task "status" "offen"]
 [?task "von-meeting" ?m]
 [?m "tag" "q3"]]
;; offene Aufgaben aus Q3-Meetings — ein Join über ?m

5 building blocks for Advanced Query

1. The rule describes the goal (:find), not the search path — you say what, not how.
2. Each :where line is a condition; shared variables connect them into a join.
3. Aggregates condense: count, sum, max, min, avg over the matched set.
4. A rule is reusable — name it, and it becomes a view for the whole team.
5. Set limits: recursive or unbounded joins need a bound, or the evaluation gets expensive.

Example: counting open tasks per project

[:find ?projekt (count ?task)
 :where
 [?task "type" "task"]
 [?task "status" "offen"]
 [?task "projekt" ?projekt]]
;; ein Report: pro Projekt die Zahl offener Aufgaben

Before and after — Simple Query vs Datalog

An honest question

How many of your reports do you rebuild every week because they connect several criteria no filter line can hold? The answer decides whether Datalog's steeper learning curve pays off for you — or whether a Simple Query already does the job.