SQL UPDATE

The UPDATE command in SQL is used to modify existing records in a database table.

Whenever you need to change stored data, such as correcting a name, updating marks, or changing a status, the UPDATE command is used.

Important:
The UPDATE command changes existing data permanently.

Understanding UPDATE

Consider a table as a register where data is already written.

Using UPDATE is similar to erasing a value in a register and writing a new one at the same place.

Example: Students Table

Why Use the UPDATE Command?

The UPDATE command is used to

Syntax

UPDATE table_name
SET column1 = value1, column2 = value2
WHERE condition;

Updating a Single Column

UPDATE students
SET marks = 92
WHERE id = 1;

Result

Only the student with id = 1 is updated.

Updating Multiple Columns

UPDATE students
SET name = 'Amit Sharma', marks = 90
WHERE id = 3;

Updating All Rows (Without WHERE)

UPDATE students
SET marks = 100;

This will update all rows in the table.
Always use WHERE unless intentionally updating every record.

Important Rules for Best Practices

Two Minute Drill