finish lecture 10

Author: afeld

Diff for: lectures/lecture_10.md

@@ -1,4 +1,4 @@
-# Lecture 10 - IN PROGRESS
+# Lecture 10
 
 **Data engineering**
 
@@ -8,12 +8,18 @@
 
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+## Why use a database?
+
+---
+
 ## Data engineering
 
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 ### [Overview](https://docs.google.com/presentation/d/1Q7Oe3CtLo4NuB4gCHPg4v-okfraLvAeVQWLZPAtejCA/edit)
 
+<!-- using Google Slides because it was easier to do diagrams/transitions there -->
+
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 ### [Example](https://docs.google.com/presentation/d/1-dr8oT9QsjrimhrFPiJQqDI91rMK28HZRsnx9wjGwlw/edit)