3.4.9. Add Data Model Check Constraints

In this chapter, you'll learn how to add check constraints to your data model.

What is a Check Constraint?#

A check constraint is a condition that must be satisfied by records inserted into a database table, otherwise an error is thrown.

For example, if you have a data model with a price property, you want to only allow positive number values. So, you add a check constraint that fails when inserting a record with a negative price value.

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How to Set a Check Constraint?#

To set check constraints on a data model, use the checks method. This method accepts an array of check constraints to apply on the data model.

For example, to set a check constraint on a price property that ensures its value can only be a positive number:

Code
1import { model } from "@medusajs/framework/utils"2
3const CustomProduct = model.define("custom_product", {4  // ...5  price: model.bigNumber(),6})7.checks([8  (columns) => `${columns.price} >= 0`,9])

The item passed in the array parameter of checks can be a callback function that accepts as a parameter an object whose keys are the names of the properties in the data model schema, and values the respective column name in the database.

The function returns a string indicating the SQL check constraint expression. In the expression, use the columns parameter to access a property's column name.

You can also pass an object to the checks method:

Code
1import { model } from "@medusajs/framework/utils"2
3const CustomProduct = model.define("custom_product", {4  // ...5  price: model.bigNumber(),6})7.checks([8  {9    name: "custom_product_price_check",10    expression: (columns) => `${columns.price} >= 0`,11  },12])

The object accepts the following properties:

• name: The check constraint's name.
• expression: A function similar to the one that can be passed to the array. It accepts an object of columns and returns an SQL check constraint expression.

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Apply in Migrations#

After adding the check constraint, make sure to generate and run migrations if you already have the table in the database. Otherwise, the check constraint won't be reflected.

To generate a migration for the data model's module then reflect it on the database, run the following command:

Terminal
❯npx medusa db:generate custom_module❯npx medusa db:migrate

The first command generates the migration under the migrations directory of your module's directory, and the second reflects it on the database.

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