Sometimes, transaction is doen in simultaneously, ie. both buyer and seller key in the same price same amount to be matched at the same time, that matching is done simultaneously, so "unknown" status is given.

By analysing the daily buy and sell activities is meaningless most the time, it just show particular days of market sentiment on the stocks only.
Nothing fruitfull result can be getting from there.

For TA, better study the charting issue over sometimes, is more meaningful than collecting daily buy and sell activities.