Intro to Databases - Speaker Deck

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Databases! Preetam Jinka March 2014 Intro to

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Me. 2nd year math major Twitter/GitHub: @PreetamJinka Website: http://preet.am/ Email: [email protected] Credit: Yugank Singhal

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Code along! https://github.com/PreetamJinka/intro-to-databases 1. Get Node.js 2. Clone the repository 3. Run npm install

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Disclaimers. ● Limited scope ● Alternatives used

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Ask questions!

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What the heck is a database? DEFINITION.

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What the heck is a database?

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Database Management Systems Systems that manage organized collections of data. From now on: “database” ⇒ DBMS

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There are tons of databases out there. What sets them apart?

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1. The structure of data. - How does the database look at data? 2. The questions you can ask. - Queries

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Types ● Relational ○ MySQL, PostgreSQL, Oracle, … ● Document stores ○ MongoDB, CouchDB, Couchbase, … ● Graph ○ Neo4j, … ● Key-value stores ○ File system, Redis, FoundationDB, … ● Search ○ Lucene, Solr, Elasticsearch, … … and a bunch of others I’m missing.

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Key-value stores Like associative arrays, dictionaries, maps, hashes, … key value "2+2" 4 1 true "foo" "bar"

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No content

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File systems! key value /etc/resolv.conf # Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8) # DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN nameserver 127.0.1.1 .gitignore ## .gitignore ## # dependencies node_modules/ # secret tokens tokens.js

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Demo!

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Redis A really fast advanced key-value store. “Data structure server” strings, hashes, lists, sets and sorted sets

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Querying Redis

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Relational databases Think “tables” By “relational,” we mean having to do with relations.

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Relational databases username first name last name bob Bob Barker alice Alice Cooper pj Preetam Jinka Languages table username language bob JavaScript alice C++ pj Go Users table

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Relational databases username first name last name bob Bob Barker alice Alice Cooper pj Preetam Jinka Languages table username language bob JavaScript alice C++ pj Go Users table Relation!

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SQL Structured Query Language This is how we interact with most, if not all, relational databases.

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Demo!

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Document databases Type of key-value stores. Values are “documents”

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Example document { "_id": "post_1", "title": "Hello, world", "content": "This is my first blog post!", "tags": ["general"] } post_1 is the “key”

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MongoDB’s collections Collections are groups of documents. They’re like tables in MongoDB’s context.

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Document database queries ● Get individual documents ● Find documents that ○ have a certain value ○ have properties that… ■ have a certain value

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Demo!

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Map-reduce Source: http://docs.mongodb.org/manual/core/map-reduce/

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Map-reduce

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Demo!

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IMPORTANT: There’s no one database to rule them all. Unfortunate. :-/

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Use the right tool for the job.

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You wouldn’t use a hash table for an ordered map, right? Please say yes :P

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Case study

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The application and the database Application Application Application Database State State State “stateless web application are far more flexible and scalable than their stateful counterparts” — Application State - We all want to be Stateless

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Database State State State web_app( ) State Web page

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Twelve-Factor App Methodology 12factor.net “Twelve-factor processes are stateless and share-nothing. Any data that needs to persist must be stored in a stateful backing service, typically a database.”

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Dude, where’s my state?

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In the database(s).

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Pro tips Write abstractions. Keep things simple. Mock and test.

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Pro tips Ask for help.

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That’s all (for now), folks! Thanks for coming! @PreetamJinka [email protected]