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Types of Data

2:45 with Andrew Chalkley

There are good reasons why your data should be categorized in to different types. In this video we'll explore some of them.

Types of Data

Here's a slightly larger list of data types than in the video.

  • Text Type Examples
    • TEXT
    • VARCHAR
  • Numeric Type Examples
    • INT
    • INTEGER
  • Date Type Examples
    • DATETIME
    • DATE
    • TIMESTAMP

Here's documentation sites for some other databases where you can see the similarities and differences in data types.

  • 0:00

    Table columns are defined in the schema to have certain data types.

  • 0:04

    A data type describes the value to be stored.

  • 0:08

    There are several data types you'll come across on a regular basis.

  • 0:11

    There are text types, numeric types and data types.

  • 0:15

    Text types are good for storing names or descriptions of things.

  • 0:20

    Numeric types are good for storing prices, ages, and quantities of things.

  • 0:26

    Dates are good for anything time related.

  • 0:30

    While this isn't a comprehensive list of data types, text, numeric, and

  • 0:34

    date types are a good starting point.

  • 0:37

    The reason we use types will become more important as we write SQL later on.

  • 0:42

    To help you envisage how its schema enforces types and

  • 0:46

    columns, you can think of the schema as a coin sorter.

  • 0:50

    A coin sorter is used to sort different types of coins into columns.

  • 0:54

    The coin sorter ensures that only the correct coin types go

  • 0:58

    into the correct column.

  • 0:59

    Like the coin sorter,

  • 1:00

    the database schema prescribes what data should go into each column of the table.

  • 1:06

    You may be asking, why even do this?

  • 1:08

    Let's look at some examples to see why it's important to have data types.

  • 1:13

    Imagine everything in this product table was just text.

  • 1:17

    The name, price, stock count, are all text.

  • 1:21

    If I wanted to sort by the current stock count, what result do you think I'd get?

  • 1:26

    Well, it'd be sorted like this.

  • 1:29

    This is because the stock count is sorted alphabetically, and not numerically.

  • 1:34

    Let's change the price and the stock count to a numeric type and

  • 1:38

    sort by stock count again.

  • 1:40

    That looks better.

  • 1:42

    Having correct data types in your database not only helps with sorting but

  • 1:46

    it also comes in handy for

  • 1:48

    many other applications such as generating the sum of all sales figures.

  • 1:53

    Generating a sum and

  • 1:54

    other mathematical operations can only be done by using with a numeric type.

  • 2:00

    Trying to do math with text is impossible.

  • 2:04

    In the case of an events table for an event planner where the new data is added

  • 2:08

    all the time, the data is retrieved in the order it was entered by default.

  • 2:14

    If the date of the event column was just text and

  • 2:16

    you attempted to sort it, it would look like this.

  • 2:20

    However if the date of the event was correctly at date type,

  • 2:24

    it would sort like this.

  • 2:27

    Understanding that column date types can affect how data is retrieved

  • 2:32

    helps people design the schema for the database.

  • 2:35

    While we're not designing the schema ourselves in this course,

  • 2:38

    understanding data types will also help us understand

  • 2:42

    how we compose the SQL queries throughout this course.

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