How to Comment — SQL Technical Interview Questions & Answers

How to Comment

How to Comment

  • -- this is a line comment (space after --). # also works in MySQL. /* block comment */ can span lines.
  • Don’t put secrets in comments in dumps. Nested /* */ can surprise you.
  • Trap: --comment without a space after -- in some clients.
  • On the example next to this theory: How to Comment: create two demo rows, then SELECT qty >= 2 ordered. Say which labels come back.

Technical Interview Tip: -- comment and /* block */

Code Examples for How to Comment

How to Comment — sample query

-- How to Comment
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;

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

How to Explain How to Comment to an Interviewer

SQL line comment?

-- then a space # also in MySQL