How to Use SQL RANK

In SQL, RANK() is a function that assigns a rank to each row of a result set based on the value of a specified column. The rank indicates the ordinal position of each row within the result set. The RANK() function is commonly used to display results in a specific order, such as from highest to lowest or vice versa.

Syntax

The syntax for the RANK() function is as follows:

RANK() OVER (
    [PARTITION BY partition_expression, ... ]
    ORDER BY sort_expression [ASC | DESC], ... 
)

Where:

• PARTITION BY is an optional clause that divides the result set into partitions. The rank is assigned within each partition separately.
• ORDER BY is a required clause that specifies the column or columns to sort the data by. You can also specify the sort order (ascending or descending) for each column.

Example

Suppose you have a table named sales with the following data:

id	product	sales
1	A	100
2	B	200
3	C	300
4	D	150
5	E	250

You can use the RANK() function to assign a rank to each row based on the sales column as follows:

SELECT id, product, sales, RANK() OVER (ORDER BY sales DESC) as rank
FROM sales;

The result set would be:

id	product	sales	rank
3	C	300	1
2	B	200	2
5	E	250	3
4	D	150	4
1	A	100	5

As you can see, the RANK() function has assigned a rank to each row based on the sales column, with the highest sales value receiving a rank of 1.

Troubleshooting Tips

• If you receive an error message that says “Windowed functions can only appear in the SELECT or ORDER BY clauses”, make sure that you have included the OVER clause after the RANK() function.
• If you receive an error message that says “The ORDER BY clause is invalid in views, inline functions, derived tables, subqueries, and common table expressions, unless TOP, OFFSET or FOR XML is also specified”, make sure that you have included the ORDER BY clause within the OVER clause.

Conclusion

The RANK() function is a powerful tool for ranking rows in a result set based on the value of a specified column. By using the PARTITION BY clause, you can also divide the result set into partitions and assign ranks within each partition separately. Remember to follow the syntax and troubleshooting tips to get the most out of the RANK() function in SQL.