First Guide to SQL Anywhere Studio
   PART 3. Basic SQL
     CHAPTER 15. Updating the Database       

Modifying rows in a table

In most databases, you need to update data stored in the database. For example, suppose that the employee named James Klobucher (employee ID 467) is transferred from the sales department to the marketing department. In SQL, this is done using the UPDATE statement:

UPDATE employee
SET dept_id = 400
WHERE emp_id = 467

The WHERE clause identifies which employee to update.

Example: using the WHERE clause 

SQL can update more than one column at a time. For example, the manager ID should change when employees are transferred between departments, as well as the department ID. The following statement carries out both updates at the same time for employee Marc Dill (employee ID 195):

UPDATE employee
SET dept_id = 400,
manager_id = 1576
WHERE emp_id = 195

The UPDATE and INSERT commands 

SQL allows more than one row to be updated at one time. For example, if a group of sales employees are transferred into marketing and have their dept_id column updated, the following statement sets the manager_id for all employees in the marketing department to 1576.

UPDATE employee
SET manager_id = 1576
WHERE dept_id = 400

For employees already in the marketing department, no change is made.

It is also possible that an UPDATE statement updates no rows. For example, suppose you had made a mistake typing the employee ID in the first UPDATE statement above:

UPDATE employee
SET dept_id = 400
WHERE emp_id = 194

No rows would be updated since there is no employee with the employee ID 194.