UPDATE table SET columnB = columnA;
//Postgres Database Query
insert into table1(column1,column2)
select c1,c2
from table2 a
where not exists ( select 0 from table1 b where b.id = a.id )
UPDATE Table2 --format schema.table_name
SET
ref_id2 = table1.ref_id1
FROM table1 -- mention schema name
WHERE table1.id = table2.id
AND
table1.a_ref1 = table2.b_ref1;