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reading-notes

CodeFellows Class Reading Notes

Questions:

Note - Several questions are the same as those from Class 03

Why would a developer choose to make data models?

Before adding data to a database, a developer would need to assess how to structure their schema (in the case of a SQL database) or how they would set up information within a collection (in the case of a NoSQL database). By making a data model, the developer would be able to get a handle on what data they are dealing with and what would be the most useful way of organizing that data within a database so that they can have a plan for what that database will actually look like.

What purpose do CRUD operations serve?

CRUD (Create, Read, Update, and Delete) describes the four functions that are necessary in any application that involve a database. This means that the application should allow one to create new entries in the database, access the information within the database, alter/update the information in the database, and remove entries from the database as needed. Without CRUD, one would not have full access to the database that they are interacting with.

Source: https://stackify.com/what-are-crud-operations/

What kind of database is Postgres? What kind of database is MongoDB?

Source: https://www.postgresql.org/about/, https://www.mongodb.com/

What is Mongoose and why do we need it?

Mongoose is an Object Document Mapper that allows one to define objects with a strongly-typed schema that is mapped to a MongoDB document. My understanding at this time is that while Mongoose is not strictly necessary to use MongoDB, it can help to bridge the gap between SQL and NoSQL data by mapping a user-defined schema onto a Mongo document.

Source: https://code.tutsplus.com/articles/an-introduction-to-mongoose-for-mongodb-and-nodejs–cms-29527

Describe how NoSQL Databases scale horizontally

Horizontal scaling means adding additional machines to handle increased load (as opposed to vertical scaling, which means adding power to the existing machine - a more expensive and ultimately limited option). Because using additional machines necessitates splitting up the data to spread the load, it doesn’t work well for SQL databases because they depend on relationships between tables and so need to be able to communicate between each other. However, because NoSQL databases are made up of self contained units they do not face this issue and lend themselves well to horizontal scaling.

Source: https://medium.com/@abhinavkorpal/scaling-horizontally-and-vertically-for-databases-a2aef778610c

Give one strong argument for and against NoSQL Databases

NoSQL Databases are excellent when you are dealing with a large amount of diverse information that could not easily be represented on a schema. NoSQL Databases are less than ideal if you know you will be frequently updating data that is stored in multiple documents (ie cross-references) because each individual iteration will need to be individually updated every time (as opposed to a SQL database which - if set up well - will depend on references rather than duplicate data)

Define three related pieces of data in a possible application. An example for a store application might be Product, Category and Department. Describe the constraints and rules on each piece of data and how you would relate these pieces to each other. For example, each Product has a Category and belongs in a Department.

In animal classifications, an Order is within a Class and contains many types of Family

Source: https://www.mensaforkids.org/teach/lesson-plans/classifying-animals/

Name 3 cloud based NoSQL Databases

Source: https://support.rackspace.com/how-to/examples-of-rdbms-and-nosql-databases/

Definitions

Note - Terms are the same as those from Class 03

Term Definition Source
database A data structure that stores organized information https://techterms.com/definition/database
data model An abstract model that organizes elements of data and standardizes how they relate to one another and ot hte properties of real-world entities https://en.wikipedia.org/wiki/Data_model
CRUD Short for Create, Read, Update and Delete - the four basic functions that models should be able to do at a bare minimum. https://www.codecademy.com/articles/what-is-crud
schema The skeleton structure that represents the logical view of the entire database - defining how data is organized and how the relations among them are associated https://www.tutorialspoint.com/dbms/dbms_data_schemas.htm
sanitize To remove illegal characters from data, for the purpose of protection from malicious data https://medium.com/@abderrahman.hamila/what-sanitize-mean-and-why-sanitize-in-code-data-5c68c9f76164
Structured Query Language (SQL) A language that allows one to write database queries. These databases use a schema and store data in tables https://www.youtube.com/watch?v=ZS_kXvOeQ5Y
Non SQL (NoSQL) Database based on collections with associated documents - unlike tables, documents do not use a schema and there are not relations (relational data would need to be merged manually) because the documents are able to hold all the necessary data. This allows for more flexibility of data https://www.youtube.com/watch?v=ZS_kXvOeQ5Y
MongoDB ‘humongous’ - a NoSQL database meant to store large amounts of data https://www.youtube.com/watch?v=ZS_kXvOeQ5Y
Mongoose An ODM library for MongoDB and Node.js which manages relationships between data, provides schema validation, and is used to translate between objects in code and the representation of those objects in MongoDB https://www.freecodecamp.org/news/introduction-to-mongoose-for-mongodb-d2a7aa593c57/
record A database entry that may contain one or more values https://techterms.com/definition/record
document Within a NoSQL database, a document is a record that contains data. Documents live within a collection https://docs.mongodb.com/manual/reference/glossary/
Object Relation Mapping (ORM) A programming technique in which a metadata descriptor is used to connect object code to a relational database https://www.techopedia.com/definition/24200/object-relational-mapping–orm

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