Run SQL statements in PL/pgSQL only if a row doesn't exist

Question

I want to do something like this in a PL/pgSQL function in Postgres 9.6:

INSERT INTO table1 (id, value) VALUES (1, \'a\') ON CONFLICT DO NOTHING;
--- If the          


        

Answer 1

Maybe you mean something like this?

INSERT INTO table1 (id, value) VALUES (1, 'a') ON CONFLICT DO NOTHING;
--- If the above statement didn't insert a new row
---   because id of 1 already existed, 
---   then run the following statements

affected_rows := SQL%ROWCOUNT;

IF affected_rows = 0 THEN
    INSERT INTO table2 (table1_id, value) VALUES (1, 'a');
    UPDATE table3 set (table1_id, time) = (1, now());
END IF