SQL · Theory

Convert()

Theory

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Convert()

If you can teach Convert() using Sara walking through Convert, you know it. If you only know the heading, you don’t.

Convert() order — meaning → one Convert step Sara can write from memory → one limit. Dumping ten features helps nobody.

Without Convert(), lab hour gets messy and Sara walking through Convert is hard to trust.

Use Convert() when Sara walking through Convert must stay clear. If a simpler SQL step works, use that instead.

Convert() miss — copy-pasting Convert without a dry-run. Fix it before you talk about advanced SQL.

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

One breath for Convert(), then Sara walking through Convert, then copy-pasting Convert without a dry-run. Sit down.

Exam tip

Board: Sara walking through Convert. Dry-run Convert(). Name the trap: copy-pasting Convert without a dry-run.

Convert() — sample query

-- Convert()
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;

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

Short notes

DefConvert() — Sara uses it for Sara walking through Convert in lab hour.
RuleConvert() → one Convert step Sara can write from memory.
RememberConvert() + the query planner (lab hour).
UseConvert() in lab hour (Sara walking through Convert).
TrapConvert() — copy-pasting Convert without a dry-run.
ExConvert() → Sara walking through Convert.

-- Convert() 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;

Convert()

Convert() — sample query

Short notes

Questions

Convert()

Convert() — sample query

Short notes

Questions