In MySQL, the UPDATE statement is used to update existing records in a table.

UPDATE Syntax

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

In the above syntax, WHERE clause specifies which row or rows will be updated,if we don't define WERE clause then all records of the table will be updated.

We have a table "employee" as below:

    employee

    id  first_name               salary       country
    .......................................................
    1   John                     10000         Canada
    2   Chris                    20000         Canada
    3   Max                      30000         Korea
    4   Jenny                    25000         Canada

UPDATE Example

The below statement will update "country" for the employee "John" in the "employee" table:

UPDATE employee
SET country='London', salary='15000'
WHERE first_name='John';

Result

    id  first_name               salary       country
    .......................................................
    1   John                     15000         London
    2   Chris                    20000         Canada
    3   Max                      30000         Korea
    4   Jenny                    25000         Canada

If we remove the WHERE clause from the above statement as below then all the records in the table "employee" table will be updated

UPDATE employee
SET country='London', salary='15000';

Result

    id  first_name               salary       country
    .......................................................
    1   John                     15000         London
    2   Chris                    15000         London
    3   Max                      15000         London
    4   Jenny                    15000         London

Hope this will help you :)