Excel is only a spreadsheet, it doesnt allow you to play with the data. Using SQL querys you can write complex reports looking for all kinds of movements or criteria using the data and volume information..
Excel is the wrong product if you want to properly play with the data for analysis. There is no way you could load all stocks and 10+ years worth of history into it, then analys it to look for trends or paturns that may indicate a future spike in price etc..
Also with SQL you can write querys to monitor all stock data day by day and flag things of itnerest to you, and pull data out into graphs for time periods you specify..
Again, depends how deep you want to go.. if you really want to dive into the data with most flexability you have to use a database.
