rank, dense_rank, row_num in SAP HANA SQL....explain each with example

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kenny eric · Answer

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Emily Foster · Answer

Certainly! I'd be delighted to explain the concepts of rank, dense_rank, and row_num in SAP HANA SQL with examples to provide a better understanding. 1. Rank: The `RANK()` function in SAP HANA SQL assigns a unique rank to each row within the result set based on the specific ordering criteria. If there are ties, i.e., two or more rows have the same value, they will receive the same rank, and the next rank will be skipped. For example: SELECT first_name, last_name, salary, RANK() OVER (ORDER BY salary DESC) AS salary_rank FROM employees; In this example, the query will assign ranks to employees based on their salaries in descending order. 2. Dense Rank: Unlike `RANK()`, the `DENSE_RANK()` function in SAP HANA SQL also assigns a unique rank to each row, but it does not skip ranks in the event of ties. If multiple rows have the same value, they will be assigned the same rank, and the next rank will continue from there. For instance: SELECT product_name, sales_amount, DENSE_RANK() OVER (ORDER BY sales_amount DESC) AS sales_rank FROM products; This query would assign dense ranks to products based on their sales amounts in descending order. 3. Row Number (ROW_NUMBER): The `ROW_NUMBER()` function in SAP HANA SQL simply returns a sequential integer number for each row within the result set, without regard to any ties or duplicate values. It provides a unique identifier for each row in the output. Here is an example: SELECT order_id, customer_id, order_date, ROW_NUMBER() OVER (ORDER BY order_date) AS row_num FROM orders; In this case, the query assigns a row number to each order based on the order date, without considering ties between dates. These ranking functions are quite useful in scenarios where you need to identify the relative position of rows based on certain criteria, such as ranking top sales, performance metrics, or any other ordered data sets. Let me know if you need further clarification or have any other questions!