Please forget about my earlier posts in this thread. I think the following is a really good link that shows my situation:
Please refer to the section of the page above: "Creating our Search Form". To be as clear as I possibly can be, I am trying to add the computed column to an existing Ext.grid.GridPanel whose columns are already filled with results such as what the "searchPresidents()" function echoes. This computed column needs to see whether any field of each row in the grid has a duplicate value compared to the corresponding field of all other rows. What I want to do is add this column that somehow performs another MySQL query based on the results of what "searchPresidents()" echoes, hypothetically. The reason for this is that the existing columns of the Ext.grid.GridPanel should stay intact with the information that it already has (via "searchPresidents()"). The best representation of what I am trying to do is do is the following:
The "SELECT column1, column2, column3 FROM sometable t2" is already in the grid. The "SELECT column1, column2, column3 FROM sometable t1 WHERE EXISTS..." is the computed column that I am talking about.
SELECT column1, column2, column3 FROM sometable t1 WHERE EXISTS (SELECT column1, column2, column3 FROM sometable t2 WHERE t2.column1 = t1.column1 OR t2.column2 = t1.column2 OR t2.column3 = "t1.column3");