Computer Science Engineering (CSE) Exam  >  Computer Science Engineering (CSE) Videos  >  Database Management System (DBMS)  >  SQL Window Function | How to write SQL Query using RANK, DENSE RANK, LEAD/LAG | SQL Queries Tutorial

SQL Window Function | How to write SQL Query using RANK, DENSE RANK, LEAD/LAG | SQL Queries Tutorial Video Lecture | Database Management System (DBMS) - Computer Science Engineering (CSE)

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FAQs on SQL Window Function - How to write SQL Query using RANK, DENSE RANK, LEAD/LAG - SQL Queries Tutorial Video Lecture - Database Management System (DBMS) - Computer Science Engineering (CSE)

1. What is a SQL window function and how is it different from a regular aggregate function?
Ans. A SQL window function is a type of function that performs a calculation across a set of table rows that are somehow related to the current row. Unlike regular aggregate functions which operate on a group of rows and return a single result, window functions operate on a subset of rows defined by a window or frame, and return a result for each row.
2. How do you use the RANK function in SQL?
Ans. The RANK function in SQL is used to assign a rank to each row within a partition of a result set. The RANK function assigns a unique rank value to each distinct row within the partition, with gaps left in the ranking when there are ties.
3. What is the purpose of the DENSE_RANK function in SQL?
Ans. The DENSE_RANK function in SQL is similar to the RANK function, but it does not leave gaps in the ranking when there are ties. Instead, it assigns a unique rank value to each distinct row within the partition, incrementing by 1 for each row.
4. How can you use the LEAD and LAG functions in SQL?
Ans. The LEAD and LAG functions in SQL are used to access data from a subsequent row (LEAD) or a previous row (LAG) within the same result set. These functions are useful for comparing values across rows or accessing data from rows that are not directly adjacent to the current row.
5. Can you provide an example of a SQL query using RANK and DENSE_RANK functions?
Ans. sql SELECT employee_name, department, salary, RANK() OVER (PARTITION BY department ORDER BY salary DESC) AS rank_by_salary, DENSE_RANK() OVER (PARTITION BY department ORDER BY salary DESC) AS dense_rank_by_salary FROM employees;
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