Databases - Getting the data

• Even if you can get access to the data
• ... it won't be organized in a way easy to model with
• Need to learn how to query the data

SQL - Entity Relationship Diagram

SQL - Entity Relationship Diagram

SQL - Functions

• Not the only function available
  • All Functions
• Can create your own
  • User Defined Functions
  • Need to be written in C/C++

SQL - Other JOINs

• There are other JOINs you need to learn
  • INNER JOIN
    • Same as a JOIN
  • CROSS JOIN
    • All rows joined with one another
  • LEFT JOIN / OUTER JOIN
    • Containns all rows from LEFT table
    • No row found on RIGHT table, values filled with NULLs
  • RIGHT JOIN
    • Same as LEFT but reversed

SQL - What Normally Happens

• SQL as Data Bank
• Use SQL queries to generate new predictors
• Pull data from SQL into Python. Perform operations then store results back in SQL
• Model building
  • Gather all the needed variables from Sql
    • Predictors
    • Response(s)
    • Each row one observation for training on
  • Combine it with data from other sources
    • Images
    • Unstructured Data that will be processed
  • Do some data preperation
  • Build a model

Homework - References 📚 and Tutorials 📓

• MariaDB
  • Documentation
  • MariaDB Knowledge Base
    • Official Tutorials
    • Functions
  • Unofficial Tutorials
• MySQL Cheatsheet