PostgreSQL Error - 39004 null_value_not_allowed Error Explained

What is error null_value_not_allowed?

PostgreSQL raises the null_value_not_allowed error (SQLSTATE 39004) when a NULL value is provided where the database expects a non NULL value. The target can be a table column with a NOT NULL constraint, a function argument declared NOT NULL, or a domain that forbids NULLs.

The server aborts the statement to preserve data integrity and prevent inconsistent rows or unexpected function results.

Fixing the error promptly keeps applications stable and analytics reliable.

What Causes This Error?

The error appears most often during INSERT or UPDATE statements that omit a required column or explicitly set it to NULL. It can also surface in PL/pgSQL when NULL is passed to a STRICT function, or when casting to a domain defined as NOT NULL.

Migrations that add new NOT NULL columns without default values trigger the error on existing data.

ETL jobs that map NULLs from external sources into constrained targets fail for the same reason.

How to Fix null_value_not_allowed

First identify the column, parameter, or domain that rejected the NULL. Provide a valid non NULL value in your statement or supply a DEFAULT in the schema. If NULLs are acceptable, alter the object to drop the NOT NULL constraint.

For bulk data loads, replace NULLs with meaningful defaults using COALESCE or staging tables.

Always test in a transaction to confirm the fix.

Common Scenarios and Solutions

Missing audit columns like created_at often cause the error. Add DEFAULT now() or include the column in INSERT statements. For JSON payloads, use json_populate_record to assign defaults before inserting.

When adding a new NOT NULL column to a large table, populate existing rows with UPDATE ...

SET new_col = default_value; then add the constraint to avoid failures.

Best Practices to Avoid This Error

Define sensible DEFAULT values when adding NOT NULL columns so legacy rows remain valid. Validate incoming data at the application layer and use CHECK constraints to catch bad values early.

In Galaxy’s SQL editor, enable linting to flag INSERT statements that omit NOT NULL columns.

Version your migrations so teammates cannot accidentally push incompatible schema changes.

Related Errors and Solutions

not_null_violation (SQLSTATE 23502) is similar but specific to table constraints. null_value_not_allowed extends the concept to functions and domains. data_exception errors like string_data_right_truncation also protect data integrity.

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