Columns that are too large also use more CPU time even if they are cached in memory. When you scan a table or index, it has to pass through the CPU, so the more data there is, the more CPU time it takes to process.

I was just looking at the database for a vendor supplied application, and was shocked to see they were using GUIDs in the form of strings as the primary keys for all tables. Each PK is stored in a varchar(36) column, and they even store the dashes in the column. :crying: