Validate Column Values With CHECK

Use a `CHECK` constraint to reject rows whose values fall outside an allowed rule.

Created Apr 26, 2026 Last updated Apr 26, 2026 0/5 supported engines validation-green 1 example 2 scenarios

Docker-validated Not currently validation-green

Example 1

Allow only non-negative inventory quantities

Both inserted rows satisfy quantity >= 0, so they are stored. A later insert such as quantity = -1 would violate the CHECK constraint and be rejected before bad data entered the table.

Validated query Shared across supported engines.

SQL

CREATE TABLE inventory (
  id INT,
  item VARCHAR(50),
  quantity INT,
  CONSTRAINT chk_inventory_quantity CHECK (quantity >= 0)
);

INSERT INTO
  inventory (id, item, quantity)
VALUES
  (1, 'Widget', 12),
  (2, 'Gadget', 0);

SELECT
  id,
  item,
  quantity
FROM
  inventory
ORDER BY
  id;

Expected result Returned rows for the shared example.

id	item	quantity
1	Widget	12
2	Gadget	0

The accepted rows and returned result are identical across supported engines.

Useful when

Where this command helps.

preventing negative quantities or prices from entering a table
keeping simple validation rules close to the data instead of only in application code

Explanation

What the command is doing.

A CHECK constraint stores a data-quality rule in the table definition. The database evaluates the rule whenever rows are inserted or updated, and rejects rows that do not satisfy it. Use CHECK for simple row-level rules such as non-negative quantities, allowed ranges, or relationships between columns in the same row.

Validate Column Values With CHECK

Allow only non-negative inventory quantities

Where this command helps.

What the command is doing.

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