How to write a trigger in Postgresql?

Question

PostgreSQL

UPD The more information I find out, the better I understand what exactly I want to get. Therefore, I decided to clarify the question by changing some details.
We have a database that has two tables:

We create another table:

In this table id_player= tourney_hand_player_statistics.id_palyer,
and the cell tourney_hand_player_range.range_p_3betmust contain all unique values lookup_hole_cards.hole_cards​​under the following conditions:
tourney_hand_player_statistics.id_gametype = 1and
tourney_hand_player_statistics.flg_p_3bet = true.
The question is: how to create a trigger that would update the value of a cell lookup_hole_cards.hole_cardswhen it is accessed?
Thank you.