How to Validate Data in MariaDB

Why should I validate data in MariaDB?

Validation catches bad rows before they break reports, enforces business rules after a bulk load, and detects physical corruption early. A quick ALTER TABLE ... VALIDATE CONSTRAINT or CHECK TABLE run is cheaper than fixing production bugs later.

What is the syntax for ALTER TABLE ... VALIDATE CONSTRAINT?

Use this statement to re-check an existing FOREIGN KEY, UNIQUE, or CHECK constraint on live data. MariaDB scans all rows and fails if any violate the rule.

Example: Validate a foreign-key constraint after a bulk import

-- Enable & validate after loading orphaned Orders rows is fixed
ALTER TABLE Orders
VALIDATE CONSTRAINT orders_customer_id_fk;


The command aborts on the first order whose customer_id is missing from Customers.

How do I run a physical table integrity check?

CHECK TABLE scans the underlying storage engine for corruption. Add modifiers to balance speed vs. depth.

Example: Quick integrity check on a hot table

CHECK TABLE Orders QUICK;


QUICK reads only the table headers, finishing in seconds even on busy ecommerce workloads.

How can I validate all tables from the command line?

mysqlcheck loops through every table, performing the same checks you would run manually. Pipe it into cron for scheduled assurance.

# Validate and auto-repair the ecommerce database nightly
mysqlcheck --databases ecommerce --check --auto-repair


Best practices for data validation

Run ALTER TABLE ... VALIDATE CONSTRAINT immediately after large migrations. Schedule mysqlcheck during low-traffic windows. Always use transactions when fixing invalid rows so you can roll back on error.

What mistakes do developers make?

Skipping validation on new constraints and trusting foreign keys are enforced are common errors. See the next section for details.

FAQs

Does validation lock the table?

ALTER TABLE ... VALIDATE CONSTRAINT acquires a shared read lock; DML can continue but DDL waits. CHECK TABLE ... EXTENDED may block writes, so plan maintenance windows.

How do I fix invalid rows?

Select the offending rows with a LEFT JOIN against the referenced table, correct or delete them, then rerun VALIDATE CONSTRAINT.