The UPDATE query in MySQL is used to modify existing records in a table. It allows you to change the values of one or more columns for one or more rows, based on certain conditions. The UPDATE command is essential for maintaining and managing the data in your database. Here’s a detailed explanation of the UPDATE query:

1. Basic Syntax

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

• table_name: The name of the table you want to update.
• column1 = value1, column2 = value2, ...: The columns you want to update and the new values you want to set.
• WHERE condition: The condition to specify which rows should be updated. This is crucial; without it, all rows in the table will be updated.

2. Updating a Single Column

You can update a single column for specific rows using the WHERE clause:

UPDATE employees
SET salary = 60000
WHERE employee_id = 3;

This query updates the salary of the employee with employee_id = 3 to 60,000.

3. Updating Multiple Columns

You can update multiple columns at once:

UPDATE employees
SET salary = 70000, department = 'HR'
WHERE employee_id = 5;

This query sets the salary to 70,000 and changes the department to 'HR' for the employee with employee_id = 5.

4. Updating All Rows

If you omit the WHERE clause, the UPDATE statement will modify all rows in the table:

UPDATE employees
SET department = 'Operations';

This query sets the department column to 'Operations' for all employees in the table.