SQL · Theory

Not Equal

Theory

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Not Equal

If you can teach Not Equal using Meera walking through Not Equal, you know it. If you only know the heading, you don’t.

Do Not Equal once by hand. one Not Equal step Meera can write from memory. Change one input. Say the new result out loud.

Not Equal exists so Meera can keep Meera walking through Not Equal correct in a viva board.

Meera ships Not Equal in a viva board. That is the use case worth saying.

Not Equal trap — skipping the failure case for Not Equal. Meera loses marks for that every viva.

After Not Equal, Meera should still remember skipping the failure case for Not Equal.

One breath for Not Equal, then Meera walking through Not Equal, then skipping the failure case for Not Equal. Sit down.

Exam tip

Board: Meera walking through Not Equal. Dry-run Not Equal. Name the trap: skipping the failure case for Not Equal.

Not Equal — sample query

-- Not Equal
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;

Not Equal: create two demo rows, then SELECT qty >= 2 ordered. Say which labels come back.

Short notes

DefNot Equal — Meera uses it for Meera walking through Not Equal in a viva board.
RuleNot Equal → one Not Equal step Meera can write from memory.
RememberNot Equal + the query planner (a viva board).
UseNot Equal in a viva board (Meera walking through Not Equal).
TrapNot Equal — skipping the failure case for Not Equal.
ExNot Equal → Meera walking through Not Equal.

-- Not Equal 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;

Not Equal

Not Equal — sample query

Short notes

Questions

Not Equal

Not Equal — sample query

Short notes

Questions