Should I Use Strings as Primary Keys in My MySQL Database?

Performance impact of using strings as primary keys in MySQL database

There are some performance disadvantages to using strings as primary keys compared to integers. The main difference is the indexing mechanism.

MySQL uses B-tree indexes to organize data in a tree structure, allowing efficient retrieval of data based on index keys. Integer primary keys are compared using simple numeric operators, allowing for fast and efficient searches and updates.

In contrast, since string primary keys involve differences in length and characters, a more complex comparison is required. This can cause insert, update, and query operations to be slower compared to integer primary keys, especially in tables with a large number of rows.

Choose the appropriate primary key

Despite the performance impact, there are situations where using a string as a primary key still makes sense. For example, if the string value itself represents the entity you want to store, such as a user's email address or mobile phone number, you can use it as the primary key. This ensures that each entity can be uniquely identified and facilitates easy retrieval of data based on these attributes.

However, be sure to consider the size of the table and the length of the string keys. Long strings can severely impact performance. If performance is a major issue, it's better to use a surrogate integer primary key and create a separate unique index on the string attribute for efficient lookups.

Additionally, using string primary keys as foreign keys in multiple tables can intensify the performance penalty. It is recommended to use low-cardinality properties as foreign keys whenever possible, which are less likely to conflict.

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