In SQL, what does the DISTINCT keyword do?

The DISTINCT keyword in SQL is used to remove duplicate records from the result set of a query. When you use DISTINCT in a SELECT statement, it ensures that each row returned is unique, effectively filtering out any duplicate entries. This is particularly useful when dealing with large datasets where you may want to see only unique values for a specific column or set of columns without repetitions.

For example, if you are querying a customer table for all different cities where customers live, using DISTINCT will return only one unique entry for each city, regardless of how many customers reside there.

In contrast, filtering records based on conditions involves using the WHERE clause, which narrows down results according to specified parameters. Sorting records in ascending order is handled by the ORDER BY clause, which organizes data based on the specified columns. Aggregating data into a single record usually involves functions like COUNT, SUM, AVG, etc., often used in conjunction with GROUP BY, rather than the DISTINCT keyword.