1248ERRORTier 2 — Caution✅ HIGH confidence

Every derived table must have its own alias

Category: Query SyntaxVersions: All MariaDB / MySQL versions

What this means

Error 1248 (SQLSTATE 42000) is raised when a derived table (a subquery used in the FROM clause) does not have an alias. The SQL standard and MySQL/MariaDB both require that every inline view in the FROM clause be aliased.

Why it happens

1A subquery in the FROM clause is missing an AS alias

How to reproduce

Using a subquery in FROM without an alias.

trigger — this will ERROR

SELECT avg_salary FROM (
  SELECT AVG(salary) AS avg_salary FROM employees
);
-- Missing alias after closing parenthesis

ERROR 1248 (42000): Every derived table must have its own alias

Fix 1: Add an alias to the derived table

Always — every subquery in FROM must have an alias.

fix

SELECT avg_salary FROM (
  SELECT AVG(salary) AS avg_salary FROM employees
) AS salary_summary;

Why this works

The alias (here salary_summary) allows the outer query to reference the derived table. The AS keyword is optional but recommended for clarity.

Sources

📚 Official docs: https://mariadb.com/kb/en/subqueries-in-a-from-clause/

🔧 Source ref: MariaDB Server error code 1248 / ER_DERIVED_MUST_HAVE_ALIAS

📖 Further reading: MariaDB Subqueries in FROM

Confidence assessment

✅ HIGH confidence

Stable.