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Types of Data

2:45 with Andrew Chalkley

There are good reasons why your data should be categorized into 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 are documentation sites for some other databases where you can see the similarities and differences in data types.

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    Table columns are defined in the schema to have certain data types. 0:00
    A data type describes the value to be stored. 0:04
    There are several data types you'll come across on a regular basis. 0:08
    There are text types, numeric types and date types. 0:11
    Text types are good for storing names or descriptions of things. 0:15
    Numeric types are good for storing prices, ages, and quantities of things. 0:20
    Dates are good for anything time related. 0:26
    While this isn't a comprehensive list of data types, text, numeric, and 0:30
    date types are a good starting point. 0:34
    The reason we use types will become more important as we write SQL later on. 0:37
    To help you envisage how a schema enforces data types in 0:42
    columns, you can think of the schema as a coin sorter. 0:46
    A coin sorter is used to sort different types of coins into columns. 0:50
    The coin sorter ensures that only the correct coin types go 0:54
    into the correct column. 0:58
    Like the coin sorter, 0:59
    the database schema prescribes what data should go into each column of the table. 1:00
    You may be asking, why even do this? 1:06
    Let's look at some examples to see why it's important to have data types. 1:08
    Imagine everything in this product table was just text. 1:13
    The name, price, stock count, are all text. 1:17
    If I wanted to sort by the current stock count, what result do you think I'd get? 1:21
    Well, it'd be sorted like this. 1:26
    This is because the stock count is sorted alphabetically, and not numerically. 1:29
    Let's change the price and the stock count to a numeric type and 1:34
    sort by stock count again. 1:38
    That looks better. 1:40
    Having correct data types in your database not only helps with sorting but 1:42
    it also comes in handy for 1:46
    many other applications such as generating the sum of all sales figures. 1:48
    Generating a sum and 1:53
    other mathematical operations can only be done by using data with a numeric type. 1:54
    Trying to do math with text is impossible. 2:00
    In the case of an events table for an event planner where the new data is added 2:04
    all the time, the data is retrieved in the order it was entered by default. 2:08
    If the date of the event column was just text and 2:14
    you attempted to sort it, it would look like this. 2:16
    However if the date of the event was correctly a date type, 2:20
    it would sort like this. 2:24
    Understanding that column data types can affect how data is retrieved 2:27
    helps people design the schema for the database. 2:32
    While we're not designing the schema ourselves in this course, 2:35
    understanding data types will also help us understand 2:38
    how we compose the SQL queries throughout this course. 2:42

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