为什么基于列的数据库查询速度更快?

I am researching on the approach to use for a new database which will be used for our new application. The amount of data won't be huge like 100 million records but will be about 10 million record before it gets archived. Will using column based approach for this much data be very useful than row based database? Why are column based database faster to query?I am researching on the approach to use for a n