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Home Forums Explain the purpose of the DISTINCT keyword in SQL and provide an example. – MindStick
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1 Answers

Aryan Kumar
Aryan Kumar 02 Jul 2023
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Sure. The DISTINCT keyword in SQL is used to remove duplicate rows from the result set of a SELECT statement. For example, let's say we have a table called products with the following columns:

  • product_id (integer)
  • product_name (string)
  • price (decimal)

If we run the following SELECT statement:

SQL

SELECT * FROM products;

The result set will contain all of the rows in the products table, including any duplicate rows.

To remove the duplicate rows, we can use the DISTINCT keyword:

SQL

SELECT DISTINCT product_name FROM products;

This will return a result set that contains only the unique product names from the products table.

Here is another example. Let's say we have two tables, customers and orders:

SQL

CREATE TABLE customers (
  id INT NOT NULL AUTO_INCREMENT,
  name VARCHAR(255) NOT NULL,
  email VARCHAR(255) NOT NULL,
  PRIMARY KEY (id)
);

CREATE TABLE orders (
  id INT NOT NULL AUTO_INCREMENT,
  customer_id INT NOT NULL,
  order_date DATETIME NOT NULL,
  total_amount DECIMAL(10,2) NOT NULL,
  PRIMARY KEY (id),
  FOREIGN KEY (customer_id) REFERENCES customers (id)
);

We can use the DISTINCT keyword to combine the results of a SELECT statement that queries the customers table with a SELECT statement that queries the orders table, and remove any duplicate rows:

SQL

SELECT DISTINCT customers.name, orders.order_date
FROM customers
INNER JOIN orders
ON customers.id = orders.customer_id;

This will return a result set that contains the unique names of all customers who have placed orders, along with the date of their most recent order.

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