Updating Data

 

Next, let’s look at how we can update our data. To do that, we use the syntax below:

 

UPDATE table_name

SET column1 = value1, column2 = value2, …

WHERE condition;

 

For instance, suppose we want to update the contact number of 'James Lee' from '516-514-6568' to '516-514-1729', we use the code

 

UPDATE employees

SET contact_number = '516-514-1729'

WHERE id = 1;

 

Here, we use the id column to identify 'James Lee'. We can also use other columns. For instance, we can write

 

WHERE years_in_company = 11

 

since there is only one employee with that number of years in the company.

 

However, if there is more than one employee with the same number of years, we’ll end up updating the contact numbers of all such employees, which is not what we want.

 

In addition, if we omit the WHERE clause, we’ll end up updating the contact numbers...