nulls

DE//AGENT currently lists 2 resources under nulls: 2 tutorials. Everything below is derived from the live registry — counts, capabilities, verification state and security posture come from the curated records, never from marketing copy.

Documented learning objectives across these resources:

• State the grain of a result set in one sentence — via The relational mental model — sets, grain, and NULL
• Explain how a join's cardinality (1:1, N:1, N:N) changes the row count of the result — via The relational mental model — sets, grain, and NULL
• Name the five correctness failure modes the SQL review rules target — via The relational mental model — sets, grain, and NULL
• Spot NULL-unsafe `NOT IN` and `=` predicates and rewrite them with NOT EXISTS — via Production gotchas — NULL traps, implicit casts, silent drift
• Make every cross-type comparison an explicit cast, not an implicit one — via Production gotchas — NULL traps, implicit casts, silent drift
• Classify a schema drift failure as hard (job error) or silent (nulls) — via Production gotchas — NULL traps, implicit casts, silent drift

These resources map to stage: Python + SQL (2). Follow the four-phase roadmap to place this topic inside a progression instead of learning it in isolation.

Every entry, its shape and its trust state — sorted by the registry's composite score. This table is the honest version of a marketing comparison: no sponsored placements, no unverifiable claims.

How scores are computed: source quality score.

Highest composite score first:

1. The relational mental model — sets, grain, and NULL score 34.15 — beginner
2. Production gotchas — NULL traps, implicit casts, silent drift score 34.15 — intermediate

Scores rank provenance, completeness and trust — read how verification works before adopting anything.

Start here if you're new: The relational mental model — sets, grain, and NULL.

• The relational mental model — sets, grain, and NULL — Before the first SELECT, build the model every later lesson uses: a query returns a set with a stated grain, a join changes that grain by its cardinality, and NULL never compares a… details
• Production gotchas — NULL traps, implicit casts, silent drift — The bugs that survive testing compare wrong instead of failing loud: NOT IN over a nullable subquery, a comparison across types left to an implicit cast, and a schema change that s… details

Adjacent topics: tutorial (2 shared).

Study path: the roadmap places this topic in a progression · the scoring model explains the numbers · the trust rule catalog shows every security check these entries passed through.