LAST_VALUE Function with PARTITION BY Clause in Oracle SQL

The LAST_VALUE Function in Oracle SQL / PLSQL is an analytical function and is used to return the last value in an ordered set of values.

If the last value in the ordered set is NULL, then LAST_VALUE function returns NULL unless we specify IGNORE NULLS.
If we specify IGNORE NULLS, then LAST_VALUE function returns the LAST NON NULL value in the ordered list, or NULL if the list contains all the NULL values.
LAST_VALUE function can be used with and without PARTITION BY clause.

Syntax for using the LAST_VALUE function in Oracle SQL / PLSQL is:

SELECT column(s)
,LAST_VALUE(column [IGNORE NULLS]) OVER ([PARTITION BY column] ORDER BY column ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING)
FROM table_name;

Example 1:

Using LAST_VALUE Function with PARTITION BY and without IGNORE NULLS Clause.

Suppose we have a table named ‘employee’ as shown below:

Employee_ID	Employee_Name	Salary	Department	Commission
101	Emp A	10000	Sales
102	Emp B	20000	IT	20
103	Emp C	28000	IT	20
104	Emp D	30000	Support	5
105	Emp E	32000	Sales	10
106	Emp F	20000	Sales	5
107	Emp G	12000	Sales
108	Emp H	12000	Support

Suppose we wish to view department wise employee_id, employee_name, department and the LAST value of commission that employees get in an ordered set, we can achieve the same as:

SELECT employee_id
       ,employee_name
       ,department
       ,LAST_VALUE(commission) OVER (PARTITION BY department
                   ORDER BY employee_id DESC
                   ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) Minimum_Commission
FROM employee;

We will get the following result:

Employee_ID	Employee_Name	Department	Minimum_Commission
103	Emp C	IT	20
102	Emp B	IT	20
107	Emp G	Sales
106	Emp F	Sales
105	Emp E	Sales
101	Emp A	Sales
108	Emp H	Support	5
104	Emp D	Support	5

Here we can see that we have fetched LAST values for the commission column department wise in descending order of ‘employee_id’, for ‘IT’ department the ‘employee_id = 102’ has 20 commission and hence is fetched against ‘IT’ department.

For ‘Sales’ department the ‘employee_id = 101’ have NULL as commission, hence NULL is fetched as LAST value against ‘Sales’ department.

For ‘Support’ department the ‘employee_id = 104’ has 5 as commission, hence 5 is fetched as LAST value against ‘Support’ department.

Example 2:

Using LAST_VALUE Function with PARTITION BY and IGNORE NULLS Clause.

Suppose we have a table named ‘employee’ as shown below:

Employee_ID	Employee_Name	Salary	Department	Commission
101	Emp A	10000	Sales
102	Emp B	20000	IT	20
103	Emp C	28000	IT	20
104	Emp D	30000	Support	5
105	Emp E	32000	Sales	10
106	Emp F	20000	Sales	5
107	Emp G	12000	Sales
108	Emp H	12000	Support

Suppose we wish to view department wise employee_id, employee_name, department and the LAST value of commission that employees get in an ordered set, we can achieve the same as:

SELECT employee_id
       ,employee_name
       ,department
       ,LAST_VALUE(commission IGNORE NULLS) OVER (PARTITION BY department
                   ORDER BY employee_id DESC
                   ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) Minimum_Commission
FROM employee;

We will get the following result:

Employee_ID	Employee_Name	Department	Minimum_Commission
103	Emp C	IT	20
102	Emp B	IT	20
107	Emp G	Sales	10
106	Emp F	Sales	10
105	Emp E	Sales	10
101	Emp A	Sales	10
108	Emp H	Support	5
104	Emp D	Support	5

Also observe that for ‘employee_id = 101’ in Sales department the LAST value encountered is NULL, but the next NON NULL value is 10 for ‘employee_id =105’ and hence 10 is fetched for ‘Sales’ department.

Similarly for ‘Support’ department, ‘employee_id = 104’ has commission of and hence 5 is fetched for other employees of ‘Support’ department.