Hi @leelakrishna.k,
If you open HDFql reference manual and search for compound, you will get many examples that illustrate how to define, write and read compounds in HDFql.
In addition, if you search on this same forum for HDFql compound, there will be a plethora of information about this topic. Examples (in C# as it seems to be the programming language you use looking at other posts you did): here and here.
That said, we will soon update HDFql examples webpage to include an example that illustrates the usage of a compound.
Hope it helps!