DELETE

First, let's understand what the DELETE FROM statement is and why it's so important. The DELETE FROM statement is used in SQL to delete one or more rows from a table. Imagine you’re managing a guest list for a big event, and you need to remove the names of people who RSVP’d but later cancelled. That’s precisely what DELETE FROM does in a database—it helps you clean up and maintain the accuracy of your data.

Let’s look at a practical example to illustrate this:

DELETE FROM celebs
WHERE twitter_handle IS NULL;

In this example, we’re dealing with a table called celebs. The goal is to delete any rows where the twitter_handle column has no data or NULL. Here’s how it works:

• DELETE FROM: This clause initiates the action to delete rows from the specified table.
• celebs: This is the name of the table from which we want to delete rows.
• WHERE: This clause allows us to specify the condition for deletion. We’re telling SQL to look for rows where the twitter_handle column is NULL.
• IS NULL: This condition checks whether a value is NULL (i.e., missing or undefined).

Think of the DELETE FROM statement as a meticulous cleaner, removing unwanted or irrelevant data based on the conditions you set.

Activity

Now, let’s put theory into practice with a hands-on activity. Roll up your sleeves and get ready to write some SQL code!

Deleting Rows

Delete all rows in the celebs table where the twitter_handle column is NULL.

First, we need to identify the rows that meet this condition. Run the following query to see the rows that will be deleted:

DELETE FROM celebs
WHERE twitter_handle IS NULL;

SELECT * FROM celebs;

After executing the DELETE FROM statement, the SELECT * FROM celebs; command will display the remaining rows in the table. This will help you verify that the rows with NULL twitter_handle have been successfully deleted.

Here's what you can expect after running these commands:

id	name	age	twitter_handle
4	Taylor Swift	33	@taylorswift13