Week 12 notes completed

CM3010 Databases and Advanced Data Techniques/Week 12/Week 12 notes.md

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+# Document databases and MongoDB
+This is a middleground between key-value DB's and RDB's.
+
+* Documents structres:
+  * less strict
+  * nested
+  * repeated
+  * order-sensitive
+
+* Less interlinking - When we treat the documents as a database, any link between documents is not relevant for retrieval, at first.
+* ... or linking less importan for retrieval.
+
+### Document formats
+* Markup languages for text
+* Markup languages for other data
+* Bespoke formats
+* JSON (JavaScript Object Notation)
+
+### JSON differences
+* Simple expresison of standar data structures
+* Useful for:
+  * Data persistence (serialization)
+  * Data exchange
+
+* Very similar to JavaScript:
+* Data types are similar (number, string, decimal)
+* We can't name variables and reuse them
+* In JSON, keys require quotes, in JS it's optional
+* No named structure/cross reference
+* Object keys take quotes in JSON
+
+## MongoDB
+* Document-oriented model
+* Distributed (by sharding, horizontal partitions)
+* Open-ish Source... (copyleft)
+* Operates on objects
+  e.g.
+  ```JS
+  movieData = [{title: "Ant-Man", year: 2015, actors: ["John", "Bob"]},
+  {title: "..."}]
+  ```
+  It's not a prescribed structure, but it's ok with MongoDB
+
+### MongoDB: INSERT
+`db.movies.insert(movieData)`
+
+### MongoDB: SELECT
+`db.movies.find({year: 2015});`
+
+`db.movies.find({title: /*Man/});`
+
+`db.movies.find({title: /*Man/, year:{$lt: 2010}});` less than 2010
+
+### MongoDB UPDATE
+`db.movies.update(
+    {title: "Ant-Man"}, <- find
+    {$set: {year: 2015}} <- update
+);`
+
+Or update many entries
+
+`db.movies.updateMany(
+    {actors: "Elvis Presley"},
+    {"actors.$": "Elvos Proslee"}
+);`
+
+Add an actor:
+
+`db.movies.update(
+    {title: "Ant-Man"},
+    {$push: {actors: "Michael John"}}
+);`
+
+### MongoDB
+* Fairly SQL-like
+* Reduces joins in treelike data
+* Integrates well into code
+* Has suffered security and reliability issues