SQL · Theory

DECIMAL

Theory

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DECIMAL

DECIMAL(10,2) is exact: 10 digits, 2 after the point — money, percentages you must not round wrongly. FLOAT/DOUBLE are approximate binary. Banks and fees: DECIMAL.

10,2 means 8 digits before the point + 2 after (total 10). Don’t guess — say ‘precision and scale’.

Trap — FLOAT for salary.

On the example next to this theory: DECIMAL: create two demo rows, then SELECT qty >= 2 ordered. Say which labels come back.

Exam tip

fee DECIMAL(10,2) NOT NULL

DECIMAL — sample query

-- DECIMAL
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;

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

Short notes

DefDECIMAL(p,s) exact number. Money uses this.
RuleNot FLOAT for currency.
TrapFLOAT salary.

-- DECIMAL 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;

DECIMAL

DECIMAL — sample query

Short notes

Questions

DECIMAL

DECIMAL — sample query

Short notes

Questions