PHP & MySQL · Lesson 7 of 11

UPDATE

Change existing rows with a carefully scoped WHERE clause.

Lesson

UPDATE changes matching rows. Always review the WHERE condition before running a statement; without it, every row may be modified. Bind values in application code and consider a transaction when an update is part of a multi-step operation. Use the primary key or another constrained identifier to target the intended record. Further guidance Use migrations to version schema changes, constraints to protect relationships, and prepared statements for every dynamic value. Scope writes with a precise condition, check affected rows, and use transactions when multiple statements must succeed together. Store credentials outside source control. Practice task: Create a fresh example for UPDATE. Predict the result before running it, then change one input and explain why the result changes. Test a normal case and one boundary or invalid case where it applies. Compare your output with the example and note one rule you would use in a real project.

Code examples

UPDATE

SQL

UPDATE profiles
SET display_name = 'Riya'
WHERE id = 7;

Expected output

The display name for profile 7 is updated

Key points

Change existing rows with a carefully scoped WHERE clause.
Use prepared statements for values and constraints for data integrity.
Scope writes carefully and verify their result.

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