Posted on Oct 11 Enumerated types, commonly known as Enums, are a fascinating topic in Mysql that often receives limited attention. Enum types allow you to define a set of valid string values for a column, offering both data integrity and readability. However, the use of Enums comes with its quirks and intricacies, particularly when performing arithmetic or aggregation operations on them.This blog post aims to shed light on this nuanced topic, providing you with a comprehensive understanding of Enums in MySQL—specifically focusing on what happens when you perform certain operations like +0, MAX(), MIN(), and AVG() on an Enum column.The information presented in this blog post is based on MySQL as of the date of publication. Please note that the behaviors and functionalities related to Enums or any other MySQL features may change in future versions. The examples and SQL queries mentioned are for educational purposes and should be used with caution in a production environment. Always make sure to test thoroughly before implementing any code or query in a live system. Neither the author nor the platform hosting this post will be responsible for any issues that arise from using the information provided herein.In MySQL, an Enum is a string object that has a value chosen from a list of permitted values defined at the time of table creation.Here, the name column can only take one of the three values: 'Apple', 'Banana', or 'Cherry'.When you define an Enum, MySQL automatically assigns a numerical index to each of its elements, starting from 1. So, in our fruits table example, 'Apple' would have an index of 1, 'Banana' an index of 2, and so on. This numeric index is crucial for understanding how Enums behave during arithmetic and aggregation operations.When you perform a +0 operation on an Enum column, MySQL automatically converts the Enum value to its numeric index.SQL Query:Result Table:Knowing the numerical index of an Enum can be useful in various scenarios:When you use the MAX() or MIN() function on an Enum column, MySQL considers the numeric index of the Enum values for the operation.SQL Query:Result Table:Average operations (AVG()) on an Enum column can be somewhat misleading. MySQL first converts the Enum to its numeric index and then calculates the average. This might not give you a meaningful result, as the numeric index does not represent the data's semantic value.SQL Query:Result Table:To explore some of the more intricate aspects of Enums, let's consider a table named tshirt_sizes. This table has a column size that includes values like 'x-large', 'large', 'medium', 'small', and 'x-small'. SQL Query:On the surface, it might seem logical to expect that an ORDER BY query on this size column would sort the sizes from the smallest to the largest or vice versa. However, that's far from what actually happens.SQL Query:Result Table:To uncover the method behind this madness, we can append +0 to the Enum column in our SQL query. This action converts the Enum values to their respective internal numeric indices.SQL Query:Result Table:When you call MAX() on this column, the result is equally perplexing. Unlike other operations, MAX() doesn't use the internal numeric index. Instead, it reverts to lexical (alphabetical) ordering.SQL Query:Result Table:Enums in MySQL are like Janus, the two-faced Roman god; they have two identities. One is the string value that you see, and the other is an internal numeric index that MySQL sees. Understanding this duality is crucial for leveraging Enums effectively and avoiding pitfalls.Enums in MySQL offer a convenient way to enforce data integrity and readability. However, when it comes to operations like +0, MAX(), MIN(), and AVG(), understanding the underlying numeric index is crucial. This can be both an advantage and a pitfall, depending on your specific use-case. As with any feature, thoughtful consideration is required to wield Enums effectively.Templates let you quickly answer FAQs or store snippets for re-use. Are you sure you want to hide this comment? It will become hidden in your post, but will still be visible via the comment's permalink. Hide child comments as well Confirm For further actions, you may consider blocking this person and/or reporting abuse Muhammad Haris Khan - Sep 22 Ganesh Deshpande - Sep 7 Leetcode - Sep 10 James Anderson - Sep 7 Once suspended, lordneic will not be able to comment or publish posts until their suspension is removed. 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