Finding High-Cardinality Columns

Kevin Feasel

2019-04-08

T-SQL

Constantine Kokkinos shows how you can find the cardinality of each column on a SQL table:

Today I was diving into some extremely wide tables, I wanted to take a quick look at things like “How many unique values does this table have in every column?”.

This can be super useful if you have a spreadsheet of results or a schema without effective normalization and you want to determine which rows are the “most unique” – or have high cardinality.

The Github gist is embedded at the bottom of the page, but I will run you through the code in case you want an explanation of how it works

Click through for the script.

Related Posts

Computing Time to Payment on Invoices

Daniel Hutmacher has a painful but realistic problem to solve: Here’s an example customer. You’ll notice right off the bat that we’re sending this customer an invoice every day on the 20th of the month. To add some complexity, the customer will arbitrarily pay parts of the invoiced amount over time, and to add insult […]

Read More

Tracking Who Changed Data

Bert Wagner is on a quest to find out who moved his cheese: Have you ever wondered who was the last person (or process) to modify a piece of data in your database? SQL Server offers plenty of system views and functions that provide insight into how your server is running and how your queries are performing. […]

Read More

Categories

April 2019
MTWTFSS
« Mar May »
1234567
891011121314
15161718192021
22232425262728
2930