Wide Tables :: Sam's Blog

Every once in a while, an idea comes along to build a table with a wide array of columns at a particular granularity. This is usually associated with “self-serve analytics” and/or an attempt to define a “source of truth” table. Wide tables, self-serve analytics, and source of truth tables aren’t inherently good or bad… but there are some considerations to this type of table that I’m going to rant about.

When I talk about a single “wide table” I’m kind of talking about a denormalized table just an especially wide one with many loosely related columns. The opposite of this would be a normalized design where one would “store different but related pieces of information in separate logical tables (called relations)”. I don’t want to linger on this topic too much but typically a denormalized scheme speeds up reads at the expense of writes, and vice versa for a normalized schema.

You work for a company that sells things. You record data on what was sold, how much was sold, what was projected to be sold, how much of that thing you had, how many distinct customers bought that thing, how quickly did you get that thing to your customer… I’m not going to hash out the full DDL for this table but you get the picture.

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