not_null_violation null value in column “…” violates not-null constraint (generated always) — 23502

Symptoms

A row supplied NULL for a column declared NOT NULL (commonly an identity/required column). PostgreSQL raises SQLSTATE 23502 (not_null_violation).

• A NOT NULL column received a NULL value.
• Common with identity columns set to OVERRIDING incorrectly, or missing values.
• The DETAIL line shows the failing row.

What the server log shows

ERROR:  null value in column "id" of relation "orders" violates not-null constraint
DETAIL:  Failing row contains (null, 2024-01-01, 42.00).

Why PostgreSQL raises this — what the manual says

Section 5.5.2 Not-Null Constraints:

“A not-null constraint simply specifies that a column must not assume the null value.”

A NOT NULL column rejects NULLs. Inserting/updating a row that leaves the column NULL (no value, an explicit NULL, or a misused identity override) violates the constraint, so PostgreSQL reports 23502.

Common causes

• Omitting a required column without a default.
• Explicitly inserting NULL into a NOT NULL column.
• Misusing OVERRIDING SYSTEM VALUE or feeding NULL to an identity column.

How to fix it

1. Provide a non-null value for the column.
2. For identity columns, let the database generate the value (don’t pass NULL).
3. Add a sensible DEFAULT if appropriate.

Related & next steps

• SQLSTATE 23502 — Not Null Violation (full reference)
• Message: null value in column violates not-null constraint
• Glossary: Identity column

Reference: PostgreSQL 18 Section 5.3 “Constraints”.