Wildcards — SQL Technical Interview Questions & Answers

Wildcards

Wildcards

  • LIKE wildcards: % any string, _ one character. Not * . In REGEXP, . and .* are different. Don’t mix the two languages.
  • ESCAPE if you need a literal %: LIKE '%10\%%' ESCAPE '\\' (messy — mention you can escape).
  • Trap: * from globbing files.
  • On the example next to this theory: Wildcards: create two demo rows, then SELECT qty >= 2 ordered. Say which labels come back.

Technical Interview Tip: LIKE 'A%' and LIKE 'A_ha'. Not *.

Code Examples for Wildcards

Wildcards — sample query

-- Wildcards
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;

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

How to Explain Wildcards to an Interviewer

LIKE any characters?

%