The SQL UPDATE statement is a powerful tool for updating data in a database. It can be used to update a single field or multiple fields in a table. When updating a unique field, it is important to ensure that the value being updated is unique and does not already exist in the table. This article will discuss how to use the SQL UPDATE statement to update a unique field in a table. It will also provide examples of how to use the statement to update a unique field.
UPDATE table_name
SET field_name = new_value
WHERE field_name = old_value
AND id = unique_id;
If you update (or insert into table), and the new inserted/updated col1 value is already being used on some row, your query should fail with unique constraint violation error.
Make your application handle this error/exception properly and there’s really no need to check the existence of this value before the update/insert. The less queries your application makes the better it is for everyone…
However, I’d like to draw your attention to the following:
You already seem to have an ID column in your table. If it’s a Primary Key column, then it’s definitely unique too. Now consider, if you really need to have two unique key columns in the table. If your application logic is based on the unique values in the col1 column, you can actually drop the ID column and turn col1 into Primary Key instead ?