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How do you update a record in a table?

Parthiban Kannan
Updated on December 2, 2025

1 min read

To update a record in a table in SQL, we use the UPDATE statement along with the SET clause to specify the new values, and a WHERE clause to identify which rows to update. Without a WHERE clause, all rows in the table would be updated, which is usually not desired.

For example, suppose we have an employees table and we want to update the salary of an employee with employee_id = 2:

🗃️
filename.sql 
UPDATE employees
SET salary = 60000
WHERE employee_id = 2;

This changes only the salary of the employee with ID 2.

You can also update multiple columns at once:

🗃️
filename.sql 
UPDATE employees
SET salary = 65000, department = 'IT'
WHERE employee_id = 2;

In a real-world scenario, I used UPDATE when maintaining customer records in a CRM system. For example, updating the status of customers from 'Prospect' to 'Active' after they made their first purchase:

🗃️
filename.sql 
UPDATE customers
SET status = 'Active'
WHERE purchase_count > 0;

Challenges I’ve faced include:

  • Forgetting the WHERE clause, which can accidentally update all rows in a table. To mitigate this, I often run a SELECT query first with the same condition to verify which rows will be affected.
  • Handling concurrent updates in large systems — multiple users updating the same row can cause conflicts. Using transactions and locking mechanisms helped prevent data inconsistency.

Limitations:

  • UPDATE can be slow on very large tables without proper indexing, especially when updating rows based on non-indexed columns.
  • Complex updates involving joins may require careful structuring to avoid unintended changes.

Alternatives or enhancements:

  • Use MERGE statements (in databases that support it) to perform an UPSERT — i.e., update if the record exists, or insert if it doesn’t.
  • In batch updates, sometimes using CTEs (Common Table Expressions) or temporary tables can simplify complex update logic.

In summary, the UPDATE statement is the standard way to modify existing data in SQL tables, and it’s essential to always validate conditions and consider performance for safe and efficient updates.

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