SQL · Theory

weekofyear()

Theory

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weekofyear()

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

weekofyear() on the board: one weekofyear step Sara can write from memory. Then say what weekofyear on Sara's board looks like after.

Without weekofyear(), lab hour gets messy and weekofyear on Sara's board is hard to trust.

Use weekofyear() when weekofyear on Sara's board must stay clear. If a simpler SQL step works, use that instead.

Don’t do this with weekofyear() — copy-pasting weekofyear without a dry-run. Interviewers spot it in ten seconds.

After weekofyear(), Sara should still remember copy-pasting weekofyear without a dry-run.

One breath for weekofyear(), then weekofyear on Sara's board, then copy-pasting weekofyear without a dry-run. Sit down.

Exam tip

For weekofyear(): definition + lab hour + one failure.

weekofyear() — sample query

-- weekofyear()
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;

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

Short notes

Defweekofyear() — Sara uses it for weekofyear on Sara's board in lab hour.
Ruleweekofyear() → one weekofyear step Sara can write from memory.
Rememberweekofyear() + the query planner (lab hour).
Useweekofyear() in lab hour (weekofyear on Sara's board).
Trapweekofyear() — copy-pasting weekofyear without a dry-run.
Exweekofyear() → weekofyear on Sara's board.

-- weekofyear() 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;

weekofyear()

weekofyear() — sample query

Short notes

Questions

weekofyear()

weekofyear() — sample query

Short notes

Questions