all about databases

1. UNTANGLING THE WEB
FALL 2017 WEEK 8 – PROJECT 2, DEEPER INTO DATABASES, ASYNCHRONOUS
JAVASCRIPT, NOTES ABOUT NODE

2. AGENDA
• Project 2 presentations
• Asynchronous javascript
• Promises
• Async/await
• Databases – SQL vs. NoSQL
• Looking more at NodeJS
• Routes and views
• How to render to the client
• A more detailed look at Cloudant programming
• Getting ready for project 3

3. PROJECT 2 PRESENTATIONS
• Keep it under 5 minutes
• Show off all the functionality in your front end
• Talk about the business model, including value proposition (pains and gains)
• Make sure you have emailed me
• A link to github
• A link to the running website
• SEO, business model canvas, value proposition canvas links

4. REVIEW OF FUNCTIONS
• A block of named code able to be called from other places
• Variables in js are untyped, so they can hold function references
• Parameters to a function can also be functions
• Anonymous function – a function that is not given a name but is rather just passed to another function

5. A FEW UTILITY FUNCTIONS WE’LL RUN INTO TODAY
• setTimeout(function, delay in ms) – delay and then call a function
• Math.random – generate a random number
• Math.ceil – round up

6. ASYNCHRONOUS JAVASCRIPT
• What’s a callback? You’ve used them before! In the maps example
• What’s a promise?
• What’s a promise chain?
• Anyone come across async/await?

7. CALLBACK EXAMPLE
• https://jsfiddle.net/3cew460a/
• https://www.youtube.com/watch?v=QqiNn3GfTMc

8. PROMISE EXAMPLE
• https://jsfiddle.net/s3m4xv1o/
• https://www.youtube.com/watch?v=VmMDG6h-bVQ

9. PROMISE CHAINING EXAMPLE
• https://jsfiddle.net/8Lf4zof3/
• https://www.youtube.com/watch?v=a1cTkiNuEwM

10. ASYNC/AWAIT
• It is an ES7 feature, so will have to use babel as a transpiler if we want to use it
• https://www.youtube.com/watch?v=COKdtOgopWQ

11. DATABASES
• SQL versus noSQL
• Flavours of SQL and noSQL
• Why use a database at all?
• Advanced database topics
• Schema design
• Replication
• Transactions

12. SQL VERSUS NOSQL
• SQL – Structured Query Language
• Relational database
• Use when you need multiple tables and
when you need to construct queries that
span those tables
• More functional than flat databases, but
also slower and more complex
• Can exist in either client or server
flavours
 NoSQL databases – anything that isn’t relational!
 MongoDB is a popular server-based flavor
 Redis is a local memory-mapped flavor
 Cloudant, couchDB, etc. there are many, many
types
 All are good for rapid, flat table access
 Avoid the complexities of relational databases
while still preserving the benefits

13. LOCAL SQL EXAMPLE – CARS DATABASE
• https://jsfiddle.net/m5rh3a83/1/
• (for more details see here: https://www.tutorialspoint.com/html5/html5_web_sql.htm)

14. MORE REALISTIC SQL EXAMPLE
• http://sqlfiddle.com/#!9/1d643/23
• (video help here: https://www.youtube.com/watch?v=DDVOMRvyAS4)

15. SQLZOO
• http://sqlzoo.net/
• Go do some exercises!
• (https://www.sqlteaching.com is an alternative if you want some more exercises)

16. MULTIPLE TABLES
• You will usually have more than one table
• If you have only one table, it is time to consider a NoSQL database
• Look on SQLZoo for the JOINS sections and make sense of that
• http://sqlzoo.net/wiki/The_JOIN_operation
• If you want more complex examples on a real database you can play here:
• http://data.stackexchange.com/stackoverflow/queries
• More about joins
• https://blog.codinghorror.com/a-visual-explanation-of-sql-joins/

17. POSTGRESSQL ON BLUEMIX
• Here’s a decent started project: https://github.com/IBM-Bluemix/compose-postgresql-helloworld-
nodejs

18. FOR PROJECT 3
• You’ll have to decide whether to use a flat database, like the cloudant example we walked through last
week, or a relational database like postgresSQL
• How do you make that decision?
• Complexity of your data
• Performance requirements
• Development difficulty

19. NODEJS
• We’ll look through:
• Package.json (review)
• App.js (the webserver)
• Routes and views

20. CONCEPTS (ALSO TO BE COVERED IN MORE DETAIL
NEXT WEEK)
• JSON and how to parse it
• http get, put, post, delete, etc. (reminder about CRUD pattern)
• Nodejs
• Require statement
• App.js

21. HOMEWORK 8 (DUE START OF CLASS NOV 1ST)
• Submit a github link with a file containing the query and results for each question
• Using the stackoverflow database here: http://data.stackexchange.com/stackoverflow/queries
• List the oldest 10 Victoria, BC users and order them by age.
• List the top 10 highest reputation users in Victoria that have answered questions with the tag javascript.
• List the top 5 Victoria developers by accepted answer percentage
• List the top 10 Victoria developers by accepted answer percentage on questions with the tag javascript

22. PROJECT 3
• If anyone needs to change groups get it figured out this week
• You’ll need to implement a database backend for your project and a chatbot
• Database should have new item, search, and delete (optionally edit) from the ui
• You’ll need to host your project on bluemix
• You’ll need to show a working demo of project 2 hooked up to these backend services