PokerTracker

I heard from my friend that column concerned string operators like lookup_actions_f.action = 'X' speed down work.
So, is there any diffence to work PT4 in two cases below:
lookup_actions_f.action = 'X'
vs
tourney_hand_summary.amt_pot_t = tourney_hand_summary.amt_pot_f

?

Both queries can use the database cache so there shouldn't be any noticeable difference. Also the two expressions you've given don't do the same thing since lookup_actions_f.action = 'X' is specific to a player wheareas tourney_hand_summary.amt_pot_t = tourney_hand_summary.amt_pot_f is specific to the hand.