Most Enterprise CRM like solutions store tables of customer-property-value instead of using one column per property.
This leads to lots of unions in advanced queries, and makes filtering harder. Some databases even calculate column block statistics to optimize these queries by doing less IO even for seeming table scans.
Why not one table with all customers and one column per property?
There are a few reasons, having to do with anything from MySQL sucking at schema alters for really big tables, to expectations of Enterprise customers.
This leads to lots of unions in advanced queries, and makes filtering harder. Some databases even calculate column block statistics to optimize these queries by doing less IO even for seeming table scans.
Why not one table with all customers and one column per property? There are a few reasons, having to do with anything from MySQL sucking at schema alters for really big tables, to expectations of Enterprise customers.