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Learn how to integrate `ENUM` data types into your GORM models for PostgreSQL and MySQL with this easy step-by-step guide.
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How to Add ENUM Types in GORM for PostgreSQL and MySQL

When working with Go's GORM (an ORM library for Golang) alongside relational databases like PostgreSQL or MySQL, you may find the need to represent specific categorical data. This is often done using ENUM types, which allow you to define a type that can be one of a specified set of values. For instance, you might want to categorize car types into "SEDAN," "HATCHBACK," and "MINIVAN." In this guide, we'll explore the steps to achieve this for both PostgreSQL and MySQL.

Defining the Problem

Imagine you are defining a PostgreSQL table schema that includes a column for car types. The basic structure looks something like this:

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Here lies the question: How can you enhance this CarType field to utilize an ENUM data type? This is essential for data integrity and ensuring that only allowed values can be inserted into the database.

Solution Overview

Step 1: Create the ENUM Type in PostgreSQL

The first step involves defining the ENUM type in your PostgreSQL database. This is done via a SQL command:

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This command will create an ENUM type named car_type, which can only contain the specified values, thereby enforcing data consistency.

Step 2: Define Your Go Model

Next, you need to adjust your Go model to match the ENUM definition in PostgreSQL. Here is how you can create a custom type and implement the necessary methods to support GORM.

Custom Type Definition

Here's an implementation you can use:

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Define the Table Model

Finally, connect your carType to the TestTable model.

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Now, the MyTable struct is properly configured to store car types as ENUM values in your PostgreSQL database.

Step 3: Handling MySQL Users

If you are using MySQL, adding ENUM types can be even simpler as you can use struct tags. Here’s how you can define your model with ENUM directly in GORM for MySQL:

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Or alternatively:

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Note on Other Databases

It's essential to know that while this guide focuses mostly on PostgreSQL and MySQL, GORM supports many database types. Make sure to double-check the documentation for specifics on other databases if you are using them.

Conclusion

Integrating ENUM types into your GORM models enhances the integrity and clarity of your database schema. By following the outlined steps for PostgreSQL or MySQL, you can ensure that your applications enforce specific categories for your data consistently. With GORM's flexibility, handling database types in Go has never been easier. Happy coding!