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 begins exactly there: you describe the relationship as a rule, and mium derives the rest.

Where the filter line ends

A filter line checks blocks one by one against fixed criteria. It cannot link across blocks, derive nothing and add nothing up. Otherwise you click multi-criteria reports together by hand from several views — and maintain them the same way. Datalog turns this around: one rule that describes relationships, and an engine that evaluates it.

Anatomy of a rule

A Datalog rule has two parts: :find says which quantity you want to see, :where lists the conditions — one per line. Variables like ?task connect the lines; when 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. Every :where line is a condition; shared variables connect them into a join.
3. Aggregates condense: count, sum, max, min, avg across the result 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 limit, otherwise 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/After — Simple Query vs. Datalog

An honest question

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