How to write trigger or function in Postgresql?

Question

PostgreSQL

I messed up something in my last question, and it turned out that you can’t add comments to it or change the question itself. So I apologize in advance for duplicating this question.
Initial data: There is a database in which there are two tables:

We need to create another table:

Where 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.
Question: How to write a trigger that would update the content tourney_hand_player_range.range_p_3betfor id_playerwhen new data for this appears id_playerin the table tourney_hand_player_statistics. Or maybe it's better to write a function that would return the data for the desired one id_playerin the form of text?