SQL · Theory

Functions

Theory

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Functions

Functions is a SQL idea you prove with a Functions dry-run, not with a slogan.

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

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

Dev ships Functions in a first job task. That is the use case worth saying.

Don’t do this with Functions — only reciting the name of Functions. Interviewers spot it in ten seconds.

After Functions, Dev should still remember only reciting the name of Functions.

Viva for Functions: what it is → one Functions step Dev can write from memory → the mistake (only reciting the name of Functions).

Exam tip

Board: a Functions dry-run. Dry-run Functions. Name the trap: only reciting the name of Functions.

Functions — sample query

-- 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;

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

Short notes

DefFunctions — Dev uses it for a Functions dry-run in a first job task.
RuleFunctions → one Functions step Dev can write from memory.
RememberFunctions + InnoDB (a first job task).
UseFunctions in a first job task (a Functions dry-run).
TrapFunctions — only reciting the name of Functions.
ExFunctions → a Functions dry-run.

-- 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;

Functions

Functions — sample query

Short notes

Questions

Functions

Functions — sample query

Short notes

Questions