SQL · Theory

Describe Table

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Describe Table

Describe Table is simple if you keep it on paper. Meera uses it for a Describe Table dry-run in a first job task.

For Describe Table, InnoDB is in play. Don’t blame it until you have traced a Describe Table dry-run.

Describe Table exists so Meera can keep a Describe Table dry-run correct in a first job task.

Meera ships Describe Table in a first job task. That is the use case worth saying.

Describe Table miss — skipping the failure case for Describe Table. Fix it before you talk about advanced SQL.

After Describe Table, Meera should still remember skipping the failure case for Describe Table.

Viva for Describe Table: what it is → one Describe Table step Meera can write from memory → the mistake (skipping the failure case for Describe Table).

Exam tip

Say Describe Table in one breath, then one Describe Table step Meera can write from memory, then skipping the failure case for Describe Table.

Describe Table — sample query

-- Describe Table
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;

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

Short notes

DefDescribe Table — Meera uses it for a Describe Table dry-run in a first job task.
RuleDescribe Table → one Describe Table step Meera can write from memory.
RememberDescribe Table + InnoDB (a first job task).
UseDescribe Table in a first job task (a Describe Table dry-run).
TrapDescribe Table — skipping the failure case for Describe Table.
ExDescribe Table → a Describe Table dry-run.

-- Describe Table 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;

Describe Table

Describe Table — sample query

Short notes

Questions

Describe Table

Describe Table — sample query

Short notes

Questions