OLAP stores data in a multidimensional cube, in SQL the data are stored in multiple tables.
Querying both data structures is relatively simple. With MDX you use the WHERE clause to effectively
slice the data cube to return your data of interest. In SQL you use the WHERE clause to return data
from a particular table. Joins can be used to put multiple tables together. If you are looking over
a large number of simulations, creating joins can be tedious, and will require prior knowledge of table
names and their locations on servers. Using MDX you can select your tables of interest without having to
know the names or locations of the underlying tables - you simply use the WHERE clause to slice out the your
simulations of interest by multiple variables - Temperature, Run, Maximum time step and so on.
In retrieving data without any further calculation on the data, both MDX and SQL are comparable.
Querying the database using SQL
Data are stored in multiple tables for each property and each simulation. The easiest
way to identify your protein of interest and it's association is to determine it's
pdb code. Once you have the pdb code you can query the Master_property_v
You can use JOINS to put multiple tables together for example the RMSDs of runs 1 to 3
of the 498K 1enh runs.
If you want o look at all the rmsd for all the 298K's and find those runs with high values for example you could use the master_rmsd_v view and select out just the 298K runs and look for values greater than 5 Angstroms RMSD using the WHERE clause (WHERE temp =298 and rmsd > 5). The master views are large tables that are generated on the fly and so can take some time to access.
If you are looking at a large set of targets and want to run the same query on a number of different tables from the set of simulations it is advisable to use a CURSOR. A cursor essentially lets you loop over every table in your set and run the set query over them. The example below shows a cursor that collates all the properties from multiple tables into one table for each simulation.