How to copy one column of a table into another table's column in PostgreSQL comparing same ID

Question

I need to copy ref_id1 from table1 TO the column ref_id2 in the table2 the two things matching will be : id (same column name), a_ref1 & b_ref1 (column names are differe

Answer 1

What you want is

UPDATE Table2
SET ref_id2 = table1.ref_id1
FROM table1
WHERE table1.id = table2.id
AND table1.a_ref1 = table2.b_ref1;

Edit This is what you actually want

As seen here (crudely)