When deciding whether to create a new index, or to split a table, it’s useful to work out the cardinality of the data to see whether it’s worth doing. It’s possible to calculate the cardinality of the data in a column before creating an index. (more…)

The knee-jerk reaction to poor query performance is ‘Create an index!’, but this is not always guaranteed to improve query performance, and in some cases can even damage it. (more…)

Cardinality refers to how many unique values a particular column contains with respect to the number of rows in that table. (more…)