I would like to add one more pt. here, as OLTP is in Normalized form, more no. of tables are scanned or referred for a single query, as through primary key and foreign key data needs to be fetched from its respective Master tables. Whereas in OLAP, as the data is in De-normailzed form, for a query the no. of tables queried are less.

For eq.:- If we have a banking appln., in OLTP env., we will have a separate table for customer personal details , Address details, its transaction details etc..Whereas in OLAP env. these all details can be stored in one sinlge table thus decreasing the scanning of multiple tables for a single record of a customer details.