Which SQL operation would you use to ensure that only specific data is affected by a query?

To ensure that only specific data is affected by a query in SQL, the WHERE clause is used to filter records based on specified conditions. By incorporating the WHERE clause, you can define criteria that data must meet to be included in the results of the query. This allows for precise control over which rows are selected, updated, or deleted based on the conditions provided.

For instance, if you want to retrieve employees with a salary greater than a certain amount, you would use a query structured with the WHERE clause to filter out all other employees not meeting that salary requirement. Without this functionality, the query would process all records, regardless of whether they meet the specified criteria, leading to potentially irrelevant or unnecessary data being included in the results.

The other operations mentioned have different purposes: GROUP BY is used for aggregating data into summary rows, ORDER BY determines the order of the results, and JOIN is used to combine rows from two or more tables based on a related column. Each of these has its specific use case, but only the WHERE clause is focused on filtering data based on specific conditions.