🌱 BasicsbeginnerCommonly used

How to filter rows with WHERE in SQL

Filter query results to only return rows that match a condition.

Table schema used in examples— A users table

CREATE TABLE users (
  id      INTEGER PRIMARY KEY,
  name    TEXT,
  email   TEXT,
  age     INTEGER,
  country TEXT,
  active  BOOLEAN
);

Filter by exact valueAll databases

SELECT name, email
FROM users
WHERE country = 'Kenya';

Returns only rows where country equals "Kenya". String values use single quotes.

Filter by numberAll databases

SELECT name, age
FROM users
WHERE age >= 18;

Returns users aged 18 or older. Numeric comparisons do not use quotes.

Multiple conditions with ANDAll databases

SELECT name, age, country
FROM users
WHERE country = 'Kenya'
  AND age >= 18
  AND active = true;

All conditions must be true for a row to be included.

Either condition with ORAll databases

SELECT name, country
FROM users
WHERE country = 'Kenya'
   OR country = 'Nigeria';

Returns rows where either condition is true.

For many OR conditions on the same column, use IN instead.

Negate with NOTAll databases

SELECT name, country
FROM users
WHERE NOT country = 'Kenya';

Returns rows where the condition is false. Equivalent to country != 'Kenya'.

Not equalAll databases

SELECT name, country
FROM users
WHERE country != 'Kenya';
-- or
WHERE country <> 'Kenya';

Both != and <> mean "not equal". Both work in most databases.

Common Mistakes

→Using = NULL instead of IS NULL (NULL comparisons always use IS NULL)
→Forgetting operator precedence — AND is evaluated before OR. Use parentheses to be explicit.
→Using double quotes for strings — use single quotes for string values