Oracle - Anti Join
Anti-join is used to make the queries run faster. It is a very powerful SQL construct Oracle offers for faster queries.
Anti-join between two tables returns rows from the first table where no matches are found in the second table. It is opposite of a semi-join. An anti-join returns one copy of each row in the first table for which no match is found.
Anti-joins are written using the NOT EXISTS or NOT IN constructs.
Let's take two tables "departments" and "customer"
SELECT departments.department_id, departments.department_name FROM departments WHERE NOT EXISTS ( SELECT 1 FROM customer WHERE customer.department_id = departments.department_id ) ORDER BY departments.department_id;
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