Understanding the DISTINCT Clause in MySQL
In MySQL, the DISTINCT clause is used in a SELECT query to remove duplicate rows from the result set. It ensures that each row returned is unique based on the columns specified in the SELECT clause.
Eliminates duplicate rows from the query result.
Can be applied to a single column or multiple columns, e.g.,
SELECT DISTINCT department_id FROM employees;Helps in analyzing unique values, such as distinct categories, names, or IDs.
Often used with aggregate functions to get counts of unique items, e.g.,
SELECT COUNT(DISTINCT department_id) FROM employees;
The DISTINCT clause is applied after filtering with WHERE but before ordering with ORDER BY, ensuring that duplicates are removed from the intermediate result set before final sorting.