SQL DELETE Statement

Understanding SQL DELETE

The DELETE statement removes rows from a table. It's a powerful — and potentially dangerous — command, especially if you forget to use a WHERE clause to specify which rows to remove.

Common SQL DELETE Interview Questions

How do you delete a specific row from a table?
What happens if you omit the WHERE clause in a DELETE statement?
How can you delete rows based on conditions from other tables?
What's the difference between DELETE and TRUNCATE?

Basic DELETE Syntax

The WHERE clause determines which rows to delete. Without it, all rows will be deleted!

Practical DELETE Examples

Example 1: Delete a Specific User

Remove a single user by their ID:

Example 2: Delete Videos with No Views

Remove videos that haven't been watched:

Example 3: Delete User Interactions

Remove all interactions for a specific video:

Example 4: Delete with Subquery

Delete rows based on conditions from other tables:

Mass Deletion (Use With Extreme Caution)

Warning: This will remove ALL rows from the table! Always use a WHERE clause unless you specifically intend to empty the entire table. Consider using TRUNCATE for full table deletion.

Best Practices for DELETE

Always use WHERE to avoid unintentional full wipes
Preview rows with SELECT before deleting
Use transactions so you can rollback if needed
Log deletions in an audit table for traceability
Test delete queries in a dev/staging environment first

Complex DELETE Examples

Delete Based on Multiple Conditions

Remove rows that meet multiple criteria:

Delete with Multiple Table Conditions

Delete based on complex relationships:

Common DELETE Patterns

Cascade Deletion

When deleting a user, you might need to remove their related data:

Cleanup Operations

Regular maintenance to remove unnecessary data:

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