CREATE CONSTANT
Synopsis
CREATE [ OR MODIFY ] CONSTANT module.name TYPE data_type [ DEFAULT value ]
Description
CREATE CONSTANT defines a named constant in a module. Constants hold configuration values (API URLs, feature flags, limits) that can differ between environments. In Mendix, constant values can be overridden per runtime configuration without changing the model.
The TYPE clause specifies the constant’s data type. Supported types include String, Integer, Long, Decimal, Boolean, and DateTime.
The optional DEFAULT clause sets the constant’s default value. This is the value used at runtime unless overridden by environment configuration.
If OR MODIFY is specified, the statement is idempotent. If the constant already exists, its type and default value are updated.
Constant values can also be overridden per deployment configuration using ALTER SETTINGS CONSTANT.
Parameters
- OR MODIFY
- Makes the statement idempotent. If the constant already exists, its definition is updated. Without this clause, creating a duplicate constant is an error.
- module.name
- The qualified name of the constant in the form
Module.ConstantName. The module must already exist. - data_type
- The constant’s data type. One of:
String,Integer,Long,Decimal,Boolean,DateTime. - DEFAULT value
- The default value for the constant. String values are single-quoted. Numeric values are bare. Boolean values are
trueorfalse.
Examples
String constant for API URL
CREATE CONSTANT MyModule.ApiBaseUrl TYPE String DEFAULT 'https://api.example.com';
Integer constant for configuration
CREATE CONSTANT MyModule.MaxRetries TYPE Integer DEFAULT 3;
Boolean feature flag
CREATE CONSTANT MyModule.EnableLogging TYPE Boolean DEFAULT true;
Idempotent with OR MODIFY
CREATE OR MODIFY CONSTANT MyModule.ApiBaseUrl TYPE String DEFAULT 'https://api.example.com/v2';
Constant without a default
CREATE CONSTANT MyModule.DatabasePassword TYPE String;
Override constant per configuration
-- Create the constant
CREATE CONSTANT MyModule.ApiBaseUrl TYPE String DEFAULT 'https://api.example.com';
-- Override in a specific runtime configuration
ALTER SETTINGS CONSTANT 'MyModule.ApiBaseUrl' VALUE 'https://staging.example.com' IN CONFIGURATION 'Staging';