SQL · Theory

SQRT()()

Theory

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SQRT()()

SQRT() is a MySQL math function — square root. SQRT(9) is 3. Use it in SELECT, e.g. SELECT SQRT(marks) FROM students;

These functions do not change stored marks unless you UPDATE. NULL in, NULL out for most of them.

Trap — mixing SQRT with TRUNCATE TABLE (different word). Trap: maths on VARCHAR without CAST.

In a viva, one numeric example beats listing twenty functions.

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

Exam tip

Explain SQRT with one number. square root. SQRT(9) is 3.

SQRT()() — sample query

-- SQRT()()
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;

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

Short notes

DefSQRT() — square root. SQRT(9) is 3.
RuleSELECT the function; UPDATE only if you mean to store it.
TrapNULL in → NULL out. Don’t confuse with table TRUNCATE.

-- SQRT()() 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;

SQRT()()

SQRT()() — sample query

Short notes

Questions

SQRT()()

SQRT()() — sample query

Short notes

Questions