How to fix 42P12: invalid_database_definition in PostgreSQL

PostgreSQLINTERMEDIATEMEDIUMUpdated Dec 26, 2025· 108 views

This error occurs when a CREATE DATABASE or ALTER DATABASE statement contains invalid syntax or parameters. Fix by verifying your database definition syntax and ensuring all options are valid.

Quick fix

Fixes 42P12: invalid_database_definition

CREATE DATABASE database_name
  WITH
  OWNER = owner_name
  ENCODING = encoding_name
  LOCALE = locale_name
  TEMPLATE = template_name;
  1. Check the CREATE DATABASE syntax
  2. Verify ENCODING and LOCALE parameters
  3. Validate the TEMPLATE parameter
  4. Check for conflicting options
postgresql — error
CREATE DATABASE database_name
  WITH
  OWNER = owner_name
  ENCODING = encoding_name
  LOCALE = locale_name
  TEMPLATE = template_name;
42P12: invalid_database_definition

What this error means

The 42P12 error indicates that PostgreSQL encountered a syntax or structural problem with a database creation or modification statement. This belongs to the "42" error class (Syntax Error or Access Rule Violation) and means your CREATE DATABASE or ALTER DATABASE command has malformed parameters, invalid option combinations, or incorrect syntax that violates PostgreSQL standards.

Typical symptoms

  • Error appears when running CREATE DATABASE or ALTER DATABASE commands
  • Application fails to create or modify database definitions
  • Migration scripts fail during database initialization
  • Database provisioning fails in automated deployment pipelines

Common causes

  1. Invalid or unsupported parameters in CREATE DATABASE statement
  2. Malformed TEMPLATE, ENCODING, or LOCALE options
  3. Invalid combination of database options (e.g., conflicting template specifications)
  4. Typos or syntax errors in database definition clauses
  5. Using reserved keywords without proper quoting
  6. Unsupported option for your PostgreSQL version

How to fix "42P12: invalid_database_definition"

1Check the CREATE DATABASE syntax

Verify your CREATE DATABASE statement matches PostgreSQL syntax. The basic form is:

sql
CREATE DATABASE database_name
  WITH
  OWNER = owner_name
  ENCODING = encoding_name
  LOCALE = locale_name
  TEMPLATE = template_name;

Ensure all options are valid and spelled correctly.

2Verify ENCODING and LOCALE parameters

Check that your ENCODING and LOCALE values are supported:

bash
# List available encodings
psql -c "SELECT name FROM pg_catalog.pg_encoding_list()"

# List available locales (on Linux)
locale -a

Use only valid encoding names like UTF8, LATIN1, and locale strings like en_US.UTF-8.

3Validate the TEMPLATE parameter

If using a TEMPLATE, ensure the template database exists:

sql
-- List available templates
SELECT datname FROM pg_database WHERE datistemplate = true;

-- Create database with valid template
CREATE DATABASE mydb TEMPLATE template0 ENCODING 'UTF8';

Common templates are template0 and template1.

4Check for conflicting options

Remove conflicting or duplicate options:

sql
-- WRONG: both LOCALE and LCCOLLATE specified incorrectly
CREATE DATABASE mydb LOCALE 'en_US' LCCOLLATE 'en_US';

-- CORRECT: use LOCALE or individual LC_* options
CREATE DATABASE mydb LOCALE 'en_US.UTF-8';

Consult your PostgreSQL version documentation for the correct option names.

5Test with a minimal CREATE statement

Start with the simplest valid CREATE DATABASE statement and add options one by one:

sql
-- Minimal: should always work
CREATE DATABASE testdb;

-- Add options gradually
CREATE DATABASE testdb ENCODING 'UTF8';
CREATE DATABASE testdb ENCODING 'UTF8' LOCALE 'C';

This helps identify which option is causing the error.

6Consult PostgreSQL documentation for your version

Error messages and supported options vary by PostgreSQL version. Check the official documentation:

- PostgreSQL 15+: https://www.postgresql.org/docs/current/sql-createdatabase.html
- PostgreSQL 13: https://www.postgresql.org/docs/13/sql-createdatabase.html
- PostgreSQL 12: https://www.postgresql.org/docs/12/sql-createdatabase.html

Ensure your options match the documentation for your specific version.

Advanced notes

In PostgreSQL, the difference between LOCALE, LC_COLLATE, and LC_CTYPE can cause confusion. LOCALE is a shorthand that sets both LC_COLLATE and LC_CTYPE together (available in PostgreSQL 10+). If you are using an older version, you may need to use LC_COLLATE and LC_CTYPE separately. Additionally, the TEMPLATE parameter is sensitive to the state of the template database—if template0 is marked as invalid, you cannot use it as a template. Use "UPDATE pg_database SET datistemplate = false WHERE datname = 'template0'" to fix this (requires superuser privileges).

Frequently asked questions

What does "42P12: invalid_database_definition" mean?
The 42P12 error indicates that PostgreSQL encountered a syntax or structural problem with a database creation or modification statement. This belongs to the "42" error class (Syntax Error or Access Rule Violation) and means your CREATE DATABASE or ALTER DATABASE command has malformed parameters, invalid option combinations, or incorrect syntax that violates PostgreSQL standards.
How do I fix "42P12: invalid_database_definition"?
This error occurs when a CREATE DATABASE or ALTER DATABASE statement contains invalid syntax or parameters. Fix by verifying your database definition syntax and ensuring all options are valid.
What causes "42P12: invalid_database_definition"?
Invalid or unsupported parameters in CREATE DATABASE statement Malformed TEMPLATE, ENCODING, or LOCALE options Invalid combination of database options (e.g., conflicting template specifications)
Is the "42P12: invalid_database_definition" error serious?
It is a medium-severity error — more of a blocker than a risk. The steps above resolve it.

Official resources & further reading