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Window Functions

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Window Functions

Meera only reaches for Window Functions when a Window Functions dry-run has to stay correct in a first job task.

Window Functions on the board: one Window Functions step Meera can write from memory. Then say what a Window Functions dry-run looks like after.

Without Window Functions, a first job task gets messy and a Window Functions dry-run is hard to trust.

Use Window Functions when a Window Functions dry-run must stay clear. If a simpler SQL step works, use that instead.

Don’t do this with Window Functions: copy-pasting Window Functions without a dry-run. Interviewers spot it in ten seconds.

Place Window Functions next to nearby SQL work — one Window Functions step Meera can write from memory is the link.

Viva for Window Functions: what it is → one Window Functions step Meera can write from memory → the mistake (copy-pasting Window Functions without a dry-run).

Exam tip

Say Window Functions in one breath, then one Window Functions step Meera can write from memory, then copy-pasting Window Functions without a dry-run.

Window Functions — sample query

-- Window Functions
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;

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

Short notes

DefWindow Functions — Meera uses it for a Window Functions dry-run in a first job task.
RuleWindow Functions → one Window Functions step Meera can write from memory.
RememberWindow Functions + InnoDB (a first job task).
UseWindow Functions in a first job task (a Window Functions dry-run).
TrapWindow Functions — copy-pasting Window Functions without a dry-run.
ExWindow Functions → a Window Functions dry-run.

-- Window Functions 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;

Window Functions

Window Functions — sample query

Short notes

Questions

Window Functions

Window Functions — sample query

Short notes

Questions