SQL First Look....

 

Entity Relationship Diagrams:


An entity relationship diagram (ERD) is a common way to view data in a database.


Why SQL


Introduction


SQL stands for Structured Query Language. It is the standard language for relational database management systems. It is especially useful in handling organized data comprised of entities (variables) and relations between different entities of the data.

There are some major advantages to using traditional relational databases, which we interact with using SQL. The five most apparent are:

  • SQL is easy to understand.
  • Traditional databases allow us to access data directly.
  • Traditional databases allow us to audit and replicate our data.
  • SQL is a great tool for analyzing multiple tables at once.
  • SQL allows you to analyze more complex questions than dashboard tools like Google Analytics.

How Databases Store Data:


Few key points about data stored in SQL databases:

  1. Data in databases is stored in tables that can be thought of just like Excel spreadsheets.
    For the most part, you can think of a database as a bunch of Excel spreadsheets. Each spreadsheet has rows and columns. Where each row holds data on a transaction, a person, a company, etc., while each column holds data pertaining to a particular aspect of one of the rows you care about like a name, location, a unique id, etc.

  2. All the data in the same column must match in terms of data type.
    An entire column is considered quantitative, discrete, or as some sort of string. This means if you have one row with a string in a particular column, the entire column might change to a text data type. This can be very bad if you want to do math with this column!

  3. Consistent column types are one of the main reasons working with databases is fast.
    Often databases hold a LOT of data. So, knowing that the columns are all of the same type of data means that obtaining data from a database can still be fast.






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Entity Relationship Diagrams

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