How to Reset a Column to NULL in SQL using UPDATE

Update and Reset a Column

Write a SQL query to reset the value of a specific column to NULL for all rows in a table.

Solution:

-- Reset the "Age" column to NULL for all employees.
UPDATE Employees -- Specify the table to update.
SET Age = NULL; -- Set the "Age" column to NULL for all rows.

Explanation:

Purpose of the Query :

• The goal is to reset the Age column to NULL for all rows in the Employees table.
• This demonstrates how to use the UPDATE statement to clear or nullify data in a specific column across an entire table.
• Key Components :
• UPDATE Employees : Specifies the table where the update will occur.
• SET Age = NULL : Resets the Age column to NULL for all rows in the table.
• Why use NULL? :
• Setting a column to NULL effectively clears its value, indicating that the data is unknown or not applicable.
• This is useful when you want to remove existing data without deleting the entire row.
• Real-World Application :
• For example, in a company database, you might reset the Age column to NULL if the data was incorrectly entered or is no longer relevant.

Additional Notes:

• Resetting a column to NULL is only possible if the column allows NULL values (i.e., it is not defined as NOT NULL).
• Scenarios where resetting a column to NULL is appropriate, such as:
• Clearing outdated or incorrect data.
• Preparing a table for new data entry by resetting specific columns.
• Important Considerations :
• Ensure that the column allows NULL values before attempting to reset it.
• Be cautious when applying this operation to large tables, as it affects all rows.

For more Practice: Solve these Related Problems:

• Write a SQL query to create a new schema with a specific authorization, assigning ownership to a designated user.
• Write a SQL query to create a schema only if it does not already exist, ensuring no error is thrown if the schema is present.
• Write a SQL query to create a new schema and set the default search path to include the newly created schema for subsequent queries.
• Write a SQL query to create a schema and grant usage privileges on it to a specific role, ensuring proper security configuration.

Have another way to solve this solution? Contribute your code (and comments) through Disqus.

Previous SQL Exercise: Insert with Auto-IncrementNext SQL Exercise: Delete with JOIN.