SQL update query using joins

When you need to update data in one table based on information from another, SQL joins come in handy. You can combine tables using a JOIN inside an UPDATE query to update values in a more dynamic and relational way.

 Basic Syntax (for most SQL databases like MySQL):

UPDATE table1

JOIN table2 ON table1.id = table2.id

SET table1.column_to_update = table2.source_column

WHERE table2.condition_column = 'some_value';

 What does this do?

• JOIN links the two tables based on a related key.
  
• SET specifies the column(s) to update in the target table.
  
• WHERE is optional but helps limit which rows are affected.
  

 Example:

Let's say you want to update employee salaries in employees using new values from a salary_updates table:

UPDATE employees e

JOIN salary_updates s ON e.emp_id = s.emp_id

SET e.salary = s.new_salary

WHERE s.effective_from <= CURDATE();

This updates only those employees whose new salary is effective today or earlier.

 Important Notes:

• The exact syntax can vary by SQL dialect (e.g., PostgreSQL uses FROM instead of JOIN in updates).
  
• Always make a backup or use a SELECT first to test your JOIN logic before running an update.
  

So yes, using joins in UPDATE queries is a powerful way to manage relational data—but always test carefully to avoid unintended changes!