SQL · Theory

Explain

Theory

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Explain

Explain sits in a first job task. Farhan’s job is Explain on Farhan's board. Write that first.

Explain on the board: one Explain step Farhan can write from memory. Then say what Explain on Farhan's board looks like after.

Skip Explain and only reciting the name of Explain shows up in a first job task.

Farhan ships Explain in a first job task. That is the use case worth saying.

If Explain on Farhan's board breaks under Explain, check only reciting the name of Explain first.

Place Explain next to nearby SQL work — one Explain step Farhan can write from memory is the link.

Close Explain with — “If I skip it, Explain on Farhan's board goes wrong like this: only reciting the name of Explain.”

Exam tip

For Explain: definition + a first job task + one failure.

Explain — sample query

-- Explain
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;

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

Short notes

DefExplain — Farhan uses it for Explain on Farhan's board in a first job task.
RuleExplain → one Explain step Farhan can write from memory.
RememberExplain + an index (a first job task).
UseExplain in a first job task (Explain on Farhan's board).
TrapExplain — only reciting the name of Explain.
ExExplain → Explain on Farhan's board.

-- Explain 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;

Explain

Explain — sample query

Short notes

Questions

Explain

Explain — sample query

Short notes

Questions