Why should you avoid using ENUMs in MySQL?

Introduction

MySQL is one of the most popular?relational database management?systems used by developers worldwide. It offers a wide range of data types, including?ENUM, which is often used to define columns that have a limited set of possible values.?

While ENUMs may seem like a convenient solution to store data efficiently, they come with a set of drawbacks that can cause problems in the long run.

In this article, we will explore why using ENUMs in MySQL may not be the best approach and provide alternative solutions to consider.

The ENUM datatype in MySQL

In MySQL, the ENUM data type is used to define a column that can have a set of pre-defined values. It allows you to specify a list of possible values that the column can hold, and each value is assigned an index number. When you insert data into an?ENUM column, you can use the?index number?or the corresponding?string value?to represent the value you want to store.

For example, if you have a column named "status" that can only have three possible values: "active", "inactive", and "pending", you can define it as an ENUM column with the following syntax:

status ENUM('active', 'inactive', 'pending')        

In this case, the value "active" is assigned index 1, "inactive" is assigned index 2, and "pending" is assigned index 3. When you insert data into the column, you can use either the index number or the string value to represent the value you want to store.

What's the big deal here?

While ENUMs may seem like a convenient way to store data with a limited set of possible values, they come with a set of disadvantages that can cause problems in the long run. In this section, we will browser some of these limitations.

Limited scalability

ENUMs can only hold a fixed set of values, which means that if you need to add more values to an ENUM column, you will have to alter the?table structure.

This alteration process can be time-consuming, especially when dealing with large tables. For example, if you have a table with millions of rows and need to add a new value to an?ENUM column, you will have to update all those rows to include the new value. This can be a slow and resource-intensive process, especially on a busy production database.

Furthermore, if you need to remove a value from an ENUM column, you will also have to alter the table, which may require updating all the rows that use that value. This can be a significant maintenance overhead, especially for large and complex databases.

In contrast, other data types like VARCHAR or?TEXT?can handle a larger number of possible values dynamically without requiring any structural changes. This makes them more scalable in situations where the set of possible values may change frequently or grow over time.

Maintenance issues

When you use ENUMs in your?database schema, it can make it difficult to maintain your codebase over time.

For example, if you need to change the set of allowed values for an?ENUM column, you will have to update all the references to that column in your code, which can be error-prone and time-consuming.

In addition, if you need to perform any changes to the structure of the ENUM column itself, such as renaming the column or changing its data type, you will have to update all the references to that column in your codebase. This can be a risky operation, especially on production databases where any mistakes can cause downtime or data loss.

Moreover, ENUMs can make it difficult to enforce consistency across your codebase. If different parts of your codebase use different values for an ENUM column, it can be challenging to maintain consistency and ensure that the data is being used correctly across all parts of the system.

Difficulty with internationalization

ENUMs can be problematic when dealing with?multilingual databases?or applications that require translations.

For example, suppose you have an?ENUM column?that stores?country names, and you want to display those names in different languages depending on the user's locale. With ENUMs, this can be difficult to achieve, as the values are stored as?fixed strings?that can't be easily translated.

One workaround for this issue is to create separate?ENUM columns?for each language and store the corresponding values in each column. However, this approach can be cumbersome and may not scale well for large databases with many languages.

How about using a?foreign key?to reference a separate table for the allowed values?

A foreign key is a type of constraint that allows you to link two tables together based on a common column. In this case, you would create a separate table to hold the allowed values for your ENUM column, and then use a foreign key to link your original table to this new table.

For example, suppose you have a table called "orders" with an ENUM column called "status" that can have values "in progress", "shipped", and "delivered". Instead of using an?ENUM?column, you could create a separate table called "order_statuses" with a single column called "name" that holds the allowed values. You would then use a foreign key to link the "orders" table to the "order_statuses" table based on the "status" column.

Using a foreign key to reference a separate table for allowed values can provide several benefits over using an ENUM column. For example:

• Increased flexibility: You can easily add or modify values over time by simply adding or modifying rows in the "order_statuses" table, without having to alter the schema of the "orders" table.
• Better query performance: Queries that join the "orders" table with the "order_statuses" table can be optimized by using indexes on the foreign key column.
• Improved scalability: By using a separate table for allowed values, you can more easily accommodate a large number of possible values, without having to alter the schema of the original table.

Conclusion

ENUMs can be a useful tool in?MySQL?for storing a limited set of values in a column. However, they also have several disadvantages that should be carefully considered when designing your database schema.

When designing your database schema, it's important to carefully consider the pros and cons of using ENUMs, as well as alternative solutions, and choose a solution that provides the best balance of performance, flexibility, and data integrity for your application. By taking a thoughtful approach to?database design, you can create a robust and efficient?data model?that meets the needs of your application and supports future growth.