Select rows with max value

In SQL, you can use the SELECT statement with the MAX() function to retrieve rows that have the maximum value in a specific column or set of columns. This is a common operation when you want to find the records with the highest or maximum values in a dataset. Let’s dive into how to write SQL queries to select rows with the maximum value.

Assume we have a table called “products” with columns “product_id” and “price,” and we want to find the product(s) with the highest price.

Using the MAX() Function with a Subquery

SELECT *
FROM products
WHERE price = (SELECT MAX(price) FROM products);

In this query, we first use a subquery to find the maximum price from the “products” table. Then, we select all rows from the “products” table where the “price” matches the maximum price found in the subquery.

Using the ORDER BY Clause

SELECT *
FROM products
ORDER BY price DESC
LIMIT 1;

In this approach, we sort the rows in descending order based on the “price” column and use the LIMIT clause to retrieve only the top row. This way, we get the row with the highest price.

Using the RANK() Window Function (for handling ties)

WITH ranked_products AS (
  SELECT *,
         RANK() OVER (ORDER BY price DESC) AS rnk
  FROM products
)
SELECT *
FROM ranked_products
WHERE rnk = 1;

This query uses the RANK() window function to assign a rank to each row based on the “price” column in descending order. Rows with the same price will have the same rank. Then, we select rows with a rank of 1, which represents the highest price.

Using a Common Table Expression (CTE) with a Self-Join

WITH max_price AS (
  SELECT MAX(price) AS max_price
  FROM products
)
SELECT p.*
FROM products p
JOIN max_price m ON p.price = m.max_price;

Here, we create a CTE (max_price) to find the maximum price. Then, we perform a self-join between the “products” table and the CTE, matching rows based on the “price” column.

These are some common SQL techniques to select rows with the maximum value in a specific column. Depending on your database system and requirements, you may choose the method that best suits your needs.

In summary, SQL allows you to use the SELECT statement with the MAX() function and appropriate filtering conditions to select rows with the maximum values in specific columns or combinations of columns in your database tables.

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