← Back to SQL Documentation

UPDATE Statement

The UPDATE statement is used to modify existing records in a table. You can update a single record or multiple records based on a specified condition.

Syntax

The basic syntax for the UPDATE statement is as follows:

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

Parameters:

• table_name: The name of the table you want to update.
• SET column1 = value1, column2 = value2, ...: Specifies the columns to update and their new values.
• WHERE condition: An optional clause that specifies which records to update. If the WHERE clause is omitted, all records in the table will be updated.

Examples

Example 1: Updating a Single Record

Suppose we have a table named Employees with columns EmployeeID, FirstName, LastName, and Salary. To increase the salary of the employee with EmployeeID = 101:

UPDATE Employees
SET Salary = 65000
WHERE EmployeeID = 101;
        

Example 2: Updating Multiple Records

To give a 10% raise to all employees in the 'Sales' department:

UPDATE Employees
SET Salary = Salary * 1.10
WHERE Department = 'Sales';
        

Example 3: Updating Multiple Columns

To update both the department and the salary for a specific employee:

UPDATE Employees
SET Department = 'Marketing',
    Salary = 72000
WHERE EmployeeID = 105;
        

Important Considerations

• Use WHERE clause cautiously: Always ensure your WHERE clause is correctly specified to avoid unintended updates to the wrong records. It's a good practice to test your UPDATE statement with a SELECT statement first to see which rows will be affected.
• Data types: Ensure that the values you provide for the columns match their respective data types.
• Constraints: Updates must adhere to any constraints defined on the table, such as primary keys, foreign keys, unique constraints, and check constraints.
• Transactions: For critical operations, consider wrapping your UPDATE statements within a transaction to allow for rollback if something goes wrong.

Common Clauses with UPDATE

While WHERE is the most common, other clauses can be used:

• FROM clause (for more complex updates involving joins):

  
  UPDATE e
  SET e.Salary = e.Salary * 1.05
  FROM Employees e
  JOIN Departments d ON e.DepartmentID = d.DepartmentID
  WHERE d.DepartmentName = 'IT';
                  

Related Topics

• INSERT Statement
• DELETE Statement
• SELECT Statement
• SQL Transactions