What purpose does the WHERE clause serve in an SQL query?

The WHERE clause is crucial in SQL queries as it adds a condition that filters results based on specific criteria. This means that when you want to retrieve data from a database, you can limit the results to only those that meet certain conditions set in the WHERE clause. For instance, if you have a table of students and want to find all students with a particular grade, you would use the WHERE clause to specify that condition, only returning records that match that grade.

Using a WHERE clause enhances the efficiency of data retrieval by narrowing down the dataset to only the relevant entries, which is especially important when dealing with large databases. This capability is essential for managing data accurately and making meaningful queries.

The other options provided reflect different functionalities within SQL: sorting the data pertains to the ORDER BY clause, joining tables involves using JOIN clauses, and deleting records is done with the DELETE statement. Each of these serves a different purpose and does not represent the function of the WHERE clause.