Split into sub-projects and clean up READMEs

README.md

@@ -1,23 +1,41 @@
 # sql-playground
 
-📚 Learning and exploring SQL (and Postgres in particular).
+📚 Learning and exploring SQL (Postgres in particular).
 
 ---
 
-## Instructions
-
-Requires: Docker
-
-1. Start a Postgres instance using Docker Compose
-    * Execute `docker-compose up --detach`
-1. Explore the database!
-    * Enter a session on the command line with `psql --username postgres --host localhost`
-1. Define some test tables and test data
-    * Apply the DDL and DML files
-    * `psql --username postgres --host localhost -f observations/observations-schema.ddl` 
-    * `psql --username postgres --host localhost -f observations/observations-data.sql` 
-1. Stop the Postgres Docker container
-    * Execute `docker-compose down`
+## Standalone sub-projects
+
+This repository illustrates different concepts, patterns and examples via standalone sub-projects. Each sub-project is
+completely independent of the others and do not depend on the root project. This _standalone sub-project constraint_
+forces the sub-projects to be complete and maximizes the reader's chances of successfully running, understanding, and
+re-using the code.
+
+The sub-projects include:
+
+### `arrays/`
+
+Showcasing the `array` SQL data type.
+
+See the README in [arrays/](arrays/).
+
+### `lag/`
+
+Showcasing the `lag` Postgres function which is a part of Postgres' windowing support.
+
+See the README in [lag/](lag/).
+
+### `docker/`
+
+Run Postgres in a Docker container using Docker Compose.
+
+See the README in [docker/](docker/).
+
+### `administration/`
+
+Exploring how to administrate Postgres via its many tools like `pg_ctl`.
+
+See the README in [administration/](administration/).
 
 ## WishList
 

postgres-administration/postgres-administration.md → administration/administration.md

@@ -1,4 +1,4 @@
-# postgres-administration
+# administration
 
 Exploring how to administrate Postgres via its many tools like `pg_ctl`.
 

arrays/arrays.md

@@ -0,0 +1,13 @@
+# arrays
+
+Showcasing the `array` SQL data type.
+
+A dataset of "observations" is used to explore the `array` data type.
+
+## Instructions
+
+* Apply the schema:
+    * `psql --username postgres --host localhost -f observations-schema.ddl`
+* Insert test data:
+    * `psql --username postgres --host localhost -f observations-data.sql`
+* Try out the queries in `observations-explore.sql` and learn about SQL arrays!

docker/README.md

@@ -0,0 +1,16 @@
+# docker
+
+Run Postgres in a Docker container using Docker Compose.
+
+## Instructions
+
+1. Start a Postgres instance using Docker Compose:
+    * `docker-compose up --detach`
+1. Explore the database! Enter a session on the command line:
+    * `psql --username postgres --host localhost`
+1. Stop the Postgres Docker container:
+    * `docker-compose down`
+
+## Referenced Material
+
+* [Docker Compose](https://docs.docker.com/compose/)

lag/lag.md

@@ -0,0 +1,18 @@
+# lag
+
+Showcasing the `lag` Postgres function which is a part of Postgres' windowing support.
+
+Specifically, I wanted to illustrate a query where each row needs to be compared to the row preceding it.
+
+## Instructions
+
+* Apply the schema: 
+    * `psql --username postgres --host localhost -f snapshots-schema.ddl`
+* Insert test data:
+    * `psql --username postgres --host localhost -f snapshots-data.sql`
+* Try out the queries `snapshots-explore.sql` and learn about `lag`!    
+
+## Referenced Material
+
+* [Postgres official docs: "Window Functions" tutorial](https://www.postgresql.org/docs/13/tutorial-window.html)
+* [Postgres official docs: "Window Functions" reference](https://www.postgresql.org/docs/13/functions-window.html)