first() — SQL Technical Interview Questions & Answers

first()

first()

  • MIN(marks) lowest value, skips NULL. SELECT name, marks FROM students WHERE marks = (SELECT MIN(marks) FROM students); can return several students who tied.
  • MIN on strings is alphabetical (collation). MIN on dates is earliest.
  • Trap: MIN as ‘first inserted row’ — it is not, unless you MIN(id).
  • On the example next to this theory: first(): create two demo rows, then SELECT qty >= 2 ordered. Say which labels come back.

Technical Interview Tip: MIN(marks) lowest score. Subquery to get those students.

Code Examples for first()

first() — sample query

-- first()
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;

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

How to Explain first() to an Interviewer

Lowest marks?

SELECT MIN(marks) FROM students