SQL · Theory

period_add()

Theory

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period_add()

Asha only reaches for period_add() when Asha walking through period_add has to stay correct in a campus project.

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

Without period_add(), a campus project gets messy and Asha walking through period_add is hard to trust.

period_add() shows up in a campus project. Name Asha walking through period_add, not “a real-world scenario”.

Don’t do this with period_add() — only reciting the name of period_add. Interviewers spot it in ten seconds.

After period_add(), Asha should still remember only reciting the name of period_add.

Close period_add() with: “If I skip it, Asha walking through period_add goes wrong like this: only reciting the name of period_add.”

Exam tip

Board: Asha walking through period_add. Dry-run period_add(). Name the trap: only reciting the name of period_add.

period_add() — sample query

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

Short notes

Defperiod_add() — Asha uses it for Asha walking through period_add in a campus project.
Ruleperiod_add() → one period_add step Asha can write from memory.
Rememberperiod_add() + the query planner (a campus project).
Useperiod_add() in a campus project (Asha walking through period_add).
Trapperiod_add() — only reciting the name of period_add.
Experiod_add() → Asha walking through period_add.

-- period_add() 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_add()

period_add() — sample query

Short notes

Questions

period_add()

period_add() — sample query

Short notes

Questions