How do you update data in a table in MySQL?

In MySQL, updating data in a table is typically done using the UPDATE statement. The UPDATE statement allows you to modify existing records in the table. Its basic syntax is as follows:

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

Here are several key points to note:

• table_name: The name of the table to update.
• SET: Followed by the column names and their new values to be assigned.
• WHERE: This clause is crucial as it specifies which records need to be updated. If the WHERE clause is omitted, all records in the table will have the specified columns updated.

Let's illustrate how to use this statement with a specific example:

Suppose we have a table named employees that contains employee information, such as employee ID (employee_id), name (name), and age (age). Now, we need to update the age of the employee with employee_id 5 to 30. We can use the following SQL statement to achieve this update:

sql
UPDATE employees
SET age = 30
WHERE employee_id = 5;

This UPDATE statement will only update the record where employee_id is 5, changing the value of the age column to 30.

If you need to update multiple fields at once, you can do the following:

sql
UPDATE employees
SET age = 30, name = 'John Doe'
WHERE employee_id = 5;

This will update both the age and name columns for the same employee.

In practice, it is crucial to ensure the accuracy of the WHERE clause to avoid inadvertently updating records that should not be modified. It is a good practice to run a SELECT query before executing the update to confirm that the records you intend to update are indeed the ones you want to modify.