Before Li's writing statisitic hierarchy.
Fixed a bug in Add()
delete unnecessary printf statements.
Refine the print format.
Better supports for scalar-aggregation.
Delete unnecessary printf statements
delete unnecessary printf statement
add two special attributes, namely ANY and NULL.
delete unnecessary printf statement
Add a special table id, namely table id for intermeidate result.
count(*) is supported now!
Refine the print method.
delete unnecessary printf statement
New test
In the processing of completing statistic manager. To be continued..