chore(kb/postgresql): improve tl;dr

.vscode/settings.json

@@ -188,6 +188,7 @@
         "posix",
         "poweroff",
         "powersave",
+        "psql",
         "pstate",
         "pulumi",
         "pvresize",

knowledge base/postgresql.md

@@ -4,7 +4,7 @@
 
 1. [TL;DR](#tldr)
 1. [Further readings](#further-readings)
-1. [Sources](#sources)
+   1. [Sources](#sources)
 
 ## TL;DR
 
@@ -13,31 +13,45 @@
 brew install 'postgresql@14'
 sudo dnf install 'postgresql' 'postgresql-server'
 sudo zypper install 'postgresql15' 'postgresql15-server'
+```
 
+```sh
 # Connect to servers via CLI client.
-psql --host "${HOSTNAME:-localhost}" --port "${PORT:-5432}" \
-  "${DATABASENAME:-root}" "${USERNAME:-root}"
+# If not given:
+# - the hostname defaults to 'localhost';
+# - the port defaults to '5432';
+# - the username defaults to the current user.
+psql 'my-db'
+psql 'my-db' 'user'
+psql 'postgresql://host:5433/my-db?sslmode=require'
+psql -U 'username' -d 'my-db' -h 'hostname' -p 'port' -W 'password'
+
+# List available databases.
+psql … --list
+
+# Execute commands.
+psql 'my-db' … -c 'select * from tableName;' -o 'out.file'
+psql 'my-db' … -c 'select * from tableName;' -H
+psql 'my-db' … -f 'commands.sql'
 ```
 
 ## Further readings
 
 - [Docker image]
 
-## Sources
-
-All the references in the [further readings] section, plus the following:
+### Sources
 
+- [psql]
 - [Connect to a PostgreSQL database]
 
 <!--
   References
   -->
 
+<!-- In-article sections -->
 <!-- Upstream -->
 [docker image]: https://github.com/docker-library/docs/blob/master/postgres/README.md
-
-<!-- In-article sections -->
-[further readings]: #further-readings
+[psql]: https://www.postgresql.org/docs/current/app-psql.html
 
 <!-- Others -->
 [connect to a postgresql database]: https://www.postgresqltutorial.com/connect-to-postgresql-database/