Lesson 5 - UPDATE and DELETE
Lesson Overview
Make revisions to the Periodic table as it was in 1900 by using the UPDATE and DELETE keywords.
Modifying Data with UPDATE and DELETE
The UPDATE statement allows you to modify existing records in a table, while the DELETE statement allows you to remove records. Both are powerful commands that should be used with caution.
Task: Update the Periodic Table
The periodic table from 1900 is missing some modern discoveries. Let's update it:
- View the periodic table before updates:
- Update an element's atomic weight:
UPDATE elements SET atomic_weight = 1.008 WHERE element = 'Hydrogen' - Delete elements that were later disproved:
DELETE FROM elements WHERE element = 'Ether' - View the periodic table after updates:
⚠️ Important: Always Use WHERE Clauses
When using UPDATE or DELETE, always include a WHERE clause to specify which records to modify. Without it, you'll update or delete ALL records in the table!
-- DANGEROUS! This deletes ALL records
DELETE FROM elements;
-- SAFE: This deletes only specific records
DELETE FROM elements WHERE element = 'Ether';Lesson Summary
In this lesson, we've learned how to use UPDATE to modify existing records and DELETE to remove records from a database. These operations are essential for maintaining and correcting data in your databases.