Page Compression is what I like to refer to as “compression for real this time” as it goes well beyond the smart storage method of row and uses patterns/repeating values to condense the stored data.
First, to gain a better understanding of this method, check out a simple representation of a page of data. This is illustrated below in Figure 1. You’ll notice that there are some repeating values (e.g. SQLR) and some repeated strings of characters (e.g. SSSLL).
I really appreciate getting an idea of what kind of data does not compress well. You’d think auto-incrementing numbers would be another scenario, but Melissa explains how that’s not necessarily the case.