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regexp_substr()

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regexp_substr()

Isha only reaches for regexp_substr() when regexp_substr on Isha's board has to stay correct in lab hour.

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

regexp_substr() exists so Isha can keep regexp_substr on Isha's board correct in lab hour.

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

If regexp_substr on Isha's board breaks under regexp_substr(), check copy-pasting regexp_substr without a dry-run first.

After regexp_substr(), Isha should still remember copy-pasting regexp_substr without a dry-run.

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

Exam tip

Say regexp_substr() in one breath, then one regexp_substr step Isha can write from memory, then copy-pasting regexp_substr without a dry-run.

regexp_substr() — sample query

-- regexp_substr()
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;

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

Short notes

Defregexp_substr() — Isha uses it for regexp_substr on Isha's board in lab hour.
Ruleregexp_substr() → one regexp_substr step Isha can write from memory.
Rememberregexp_substr() + the query planner (lab hour).
Useregexp_substr() in lab hour (regexp_substr on Isha's board).
Trapregexp_substr() — copy-pasting regexp_substr without a dry-run.
Exregexp_substr() → regexp_substr on Isha's board.

-- regexp_substr() 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;

regexp_substr()

regexp_substr() — sample query

Short notes

Questions

regexp_substr()

regexp_substr() — sample query

Short notes

Questions