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period_diff()

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period_diff()

Priya only reaches for period_diff() when period_diff on Priya's board has to stay correct in a viva board.

Keep period_diff() small. Priya should finish period_diff on Priya's board in a few lines, not a 40-line dump.

period_diff() exists so Priya can keep period_diff on Priya's board correct in a viva board.

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

period_diff() trap — skipping the failure case for period_diff. Priya loses marks for that every viva.

Place period_diff() next to nearby SQL work — one period_diff step Priya can write from memory is the link.

Viva for period_diff(): what it is → one period_diff step Priya can write from memory → the mistake (skipping the failure case for period_diff).

Exam tip

Board: period_diff on Priya's board. Dry-run period_diff(). Name the trap: skipping the failure case for period_diff.

period_diff() — sample query

-- period_diff()
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;

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

Short notes

Defperiod_diff() — Priya uses it for period_diff on Priya's board in a viva board.
Ruleperiod_diff() → one period_diff step Priya can write from memory.
Rememberperiod_diff() + an index (a viva board).
Useperiod_diff() in a viva board (period_diff on Priya's board).
Trapperiod_diff() — skipping the failure case for period_diff.
Experiod_diff() → period_diff on Priya's board.

-- period_diff() 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;

period_diff()

period_diff() — sample query

Short notes

Questions

period_diff()

period_diff() — sample query

Short notes

Questions