title: Replace NULL in my Table with <SOME VALUE> in PostgreSQL
body: <p>Upon searching ways to replace NULL values in my table with 0 on Stack Overflow, it appears that many threads I've found point to using the COALESCE function. E.g. <a href="https://stackoverflow.com/questions/11007009/postgresql-return-0-if-returned-value-is-null">postgresql return 0 if returned value is null</a></p>
  
  <p>I understand that the COALESCE function "replaces" null values for your specific query; however, the table itself remains untouched. That is, if you queried the table again in a separate query without COALESCE, null values would still exist.</p>
  
  <p><strong>My question is, is there a way for me to replace NULL values permanently in my table with a specified value (like 0) so I don't have to COALESCE in every query? And as an extension to my question, is it considered bad practice to modify the original table instead of doing manipulations in queries?</strong></p>