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NULLIF()

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NULLIF()

If you can teach NULLIF() using NULLIF on Asha's board, you know it. If you only know the heading, you don’t.

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

NULLIF() exists so Asha can keep NULLIF on Asha's board correct in a viva board.

NULLIF() shows up in a viva board. Name NULLIF on Asha's board, not “a real-world scenario”.

NULLIF() trap — copy-pasting NULLIF without a dry-run. Asha loses marks for that every viva.

After NULLIF(), Asha should still remember copy-pasting NULLIF without a dry-run.

Close NULLIF() with: “If I skip it, NULLIF on Asha's board goes wrong like this: copy-pasting NULLIF without a dry-run.”

Exam tip

For NULLIF(): definition + a viva board + one failure.

NULLIF() — sample query

-- NULLIF()
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;

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

Short notes

DefNULLIF() — Asha uses it for NULLIF on Asha's board in a viva board.
RuleNULLIF() → one NULLIF step Asha can write from memory.
RememberNULLIF() + InnoDB (a viva board).
UseNULLIF() in a viva board (NULLIF on Asha's board).
TrapNULLIF() — copy-pasting NULLIF without a dry-run.
ExNULLIF() → NULLIF on Asha's board.

-- NULLIF() 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;

NULLIF()

NULLIF() — sample query

Short notes

Questions

NULLIF()

NULLIF() — sample query

Short notes

Questions