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Oracle Anti JoinAnti-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. Example Let's take two tables "departments" and "customer" Departments table CREATE TABLE "DEPARTMENTS" ( "DEPARTMENT_ID" NUMBER(10,0) NOT NULL ENABLE, "DEPARTMENT_NAME" VARCHAR2(50) NOT NULL ENABLE, CONSTRAINT "DEPARTMENTS_PK" PRIMARY KEY ("DEPARTMENT_ID") ENABLE ) / Customer table CREATE TABLE "CUSTOMER" ( "CUSTOMER_ID" NUMBER, "FIRST_NAME" VARCHAR2(4000), "LAST_NAME" VARCHAR2(4000), "DEPARTMENT_ID" NUMBER ) / Execute this query 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; Output
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