Add Connect To A Database By Color as a Heroku TIL

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
 
-_1444 TILs and counting..._
+_1445 TILs and counting..._
 
 ---
 
@@ -390,6 +390,7 @@ _1444 TILs and counting..._
 
 ### Heroku
 
+- [Connect To A Database By Color](heroku/connect-to-a-database-by-color.md)
 - [Deploy A Review App To A Different Stack](heroku/deploy-a-review-app-to-a-different-stack.md)
 - [Diagnose Problems In A Heroku Postgres Database](heroku/diagnose-problems-in-a-heroku-postgres-database.md)
 - [Open Dashboard For Specific Add-On](heroku/open-dashboard-for-specific-add-on.md)

heroku/connect-to-a-database-by-color.md

@@ -0,0 +1,29 @@
+# Connect To A Database By Color
+
+All of your PostgreSQL databases in Heroku are given attachment names that use
+a random color. This might be _pink_, _brown_, _cobalt_, etc. And the
+attachment names then look like `HEROKU_POSTGRESQL_PINK`,
+`HEROKU_POSTGRESQL_BROWN`, `HEROKU_POSTGRESQL_COBALT`, etc.
+
+We can connect to a Heroku-managed PostgreSQL instance from the command-line
+like so:
+
+```bash
+$ heroku pg:psql --app my-app
+```
+
+This is going to connect to the _default_ database which is the one with the
+`DATABASE_URL` attachment.
+
+There are lots of instances where we may have other databases besides the
+primary (e.g. let's say we have a read replica follower). If we want to connect
+to that one, we can do so by _color_.
+
+If that database's attachment is `HEROKU_POSTGRESQL_IVORY`, then we'd connect
+to it like so:
+
+```bash
+$ heroku pg:psql ivory --app my-app
+```
+
+[source](https://devcenter.heroku.com/articles/managing-heroku-postgres-using-cli#pg-psql)