Index Selectivity
Introduction In this article, we are going to see how Index Selectivity works in relational database systems and why the database Optimizer might choose to avoid using an index if the number of matching records is large. Index selectivity is inversely proportional to the number of index entries matched by a given value. So, a unique index has the highest selectivity because only a single entry can be matched by any given value. On the other hand, if column values are skewed, then a column value matching a large number of table… Read More
Default Database Primary, Foreign, and Unique Key Indexing
Introduction In this article, we are going to see what is the default database Primary, Foreign, and Unique Key indexing strategy when using Oracle, SQL Server, PostgreSQL, and MySQL. So, if you are wondering whether one of those top relational databases creates a default index whenever you are adding a Primary Key, Foreign Key, or Unique Key constraint, then this article is going to provide you with the answer you’ve been waiting for.
How to index JSON columns using MySQL
Introduction In this article, I’m going to explain how we can index JSON columns when using MySQL. While other relational database systems provide GIN (Generalized Inverted Index) indexes, MySQL allows you to index a virtual column that mirrors the JSON path expression you are interested in indexing.
