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

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A data type describes
the value to be stored.

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

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There are text types,
numeric types and date types.

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

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

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Dates are good for anything time related.

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

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date types are a good starting point.

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

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To help you envisage how a
schema enforces data types in

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

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

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The coin sorter ensures that
only the correct coin types go

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into the correct column.

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Like the coin sorter,

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

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You may be asking, why even do this?

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

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Imagine everything in this
product table was just text.

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

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

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Well, it'd be sorted like this.

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

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

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sort by stock count again.

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That looks better.

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

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it also comes in handy for

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

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Generating a sum and

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

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Trying to do math with text is impossible.

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

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

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If the date of the event
column was just text and

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

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

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it would sort like this.

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Understanding that column data types
can affect how data is retrieved

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helps people design the schema for
the database.

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

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understanding data types
will also help us understand

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how we compose the SQL queries
throughout this course.