Belayer questions

Belayer answers

• How to make a PostgreSQL constraint only apply to a new value
• PostgreSQL - Delete duplicated records - ERROR: too many range table entries
• pl /sql set ORA-00922: missing or invalid option on set serveroutput on;
• postgres: How to generically make a column immutable?
• Rename column only if exists
• Postgres ON CONFLICT DO UPDATE only non null values in python