I see that you are using QlikView desktop with 2 gb RAM, as you say further down. This is most certainly the reason for the long reload time.
There are a few other things to consider here:
First of all you have to consider the rate of transfer from the SQL database. If the network connection is slow then reading from the DB will be slow. Transferring 20 gb og data over a 10 mbit line will take 4,5 hours no matter how much RAM you have.
Secondly: QlikView stores data by only keeping one instance of every distinct value. eg. if you have a date field with time stamps you can have hundreds of thousands of distinct values for the Date Field. This will explode the memory/Disk usage. I do not know whether QlikView reduces the size of the tables on the fly or whether it waits until the load is complete. If it is the first case then you might have some luck reducing the number of distinct values in your query. If you have a datefield with time stamps - consider splitting it up into one DateField and one TimeField while rounding the time to some accuracy.
But no matter how you look at it 2GB of RAM is not enough to load 20 GB of data quickly, because as soon as the 2 GB is full - the application starts swapping to disk. I will not explain it more than to say that this is extremely slow and can only be fixed with more RAM or smaller data sets.
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