Description: High cardinality refers to a column in a database that has a large number of unique values. This concept is fundamental in database design and SQL query optimization, as columns with high cardinality can significantly influence query performance. For example, a column storing user identifiers, where each user has a unique ID, is considered high cardinality. In contrast, a column storing order status (such as ‘pending’, ‘shipped’, or ‘canceled’) would have low cardinality, as it has a limited number of unique values. High cardinality is relevant because it can affect how columns are indexed and how queries are executed. Indexes on high cardinality columns tend to be more effective, as they allow the database to quickly locate the desired records. However, they may also require more storage space and maintenance time. Therefore, understanding the cardinality of columns is essential for optimizing database performance and ensuring that queries run efficiently.
