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.

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

DATABASE

SQL

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Anti Join

Oracle Anti Join