SQL · Theory

GREATEST()()

Theory

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GREATEST()()

Don’t start GREATEST()() (math) with jargon. Start with a GREATEST math dry-run. That is the whole point.

Do GREATEST()() (math) once by hand. one GREATEST math step Neha can write from memory. Change one input. Say the new result out loud.

Without GREATEST()() (math), lab hour gets messy and a GREATEST math dry-run is hard to trust.

Neha ships GREATEST()() (math) in lab hour. That is the use case worth saying.

Don’t do this with GREATEST()() (math): skipping the failure case for GREATEST math. Interviewers spot it in ten seconds.

Place GREATEST()() (math) next to nearby SQL work — one GREATEST math step Neha can write from memory is the link.

Close GREATEST()() (math) with: “If I skip it, a GREATEST math dry-run goes wrong like this: skipping the failure case for GREATEST math.”

Exam tip

For GREATEST()() (math): definition + lab hour + one failure.

GREATEST()() — sample query

-- GREATEST()()
CREATE TABLE demo (
  id INTEGER PRIMARY KEY,
  label TEXT NOT NULL,
  qty INTEGER DEFAULT 0
);
INSERT INTO demo (id, label, qty) VALUES
  (1, 'alpha', 2),
  (2, 'beta', 5);
SELECT label, qty FROM demo WHERE qty >= 2 ORDER BY qty DESC;

GREATEST()(): create two demo rows, then SELECT qty >= 2 ordered. Say which labels come back.

Short notes

DefGREATEST()() (math) — Neha uses it for a GREATEST math dry-run in lab hour.
RuleGREATEST()() (math) → one GREATEST math step Neha can write from memory.
RememberGREATEST()() (math) + the query planner (lab hour).
UseGREATEST()() (math) in lab hour (a GREATEST math dry-run).
TrapGREATEST()() (math) — skipping the failure case for GREATEST math.
ExGREATEST()() (math) → a GREATEST math dry-run.

-- GREATEST()() CREATE TABLE demo ( id INTEGER PRIMARY KEY, label TEXT NOT NULL, qty INTEGER DEFAULT 0 ); INSERT INTO demo (id, label, qty) VALUES (1, 'alpha', 2), (2, 'beta', 5); SELECT label, qty FROM demo WHERE qty >= 2 ORDER BY qty DESC;

GREATEST()()

GREATEST()() — sample query

Short notes

Questions

GREATEST()()

GREATEST()() — sample query

Short notes

Questions