LAST_VALUE Function without PARTITION BY Clause in Oracle SQL – PLSQL

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.

  1. If the last value in the ordered set is NULL then LAST_VALUE function returns NULL unless we specify IGNORE NULLS.
  2. If we specify IGNORE NULLS then LAST_VALUE function returns the first NON NULL value in the ordered list, or NULL if the list contains all the NULL values.
  3. 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 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 the 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 (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
108 Emp H Support
107 Emp G Sales
106 Emp F Sales
105 Emp E Sales
104 Emp D Support
103 Emp C IT
102 Emp B IT
101 Emp A Sales

Here we can see that we have fetched NULL values in the ‘Minimum_Commission’ column because we have sorted the list in descending order of ‘employee_id’, and for ‘employee_id = 101’ the ‘commission’ is NULL, hence NULL becomes the last value that is encountered and is therefore fetched.


Example 2:

Using LAST_VALUE Function With 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 the 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 (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
108 Emp H Support 20
107 Emp G Sales 20
106 Emp F Sales 20
105 Emp E Sales 20
104 Emp D Support 20
103 Emp C IT 20
102 Emp B IT 20
101 Emp A Sales 20

Here we can see that we have fetched 20 as the commission value even though the last value encountered was NULL by using IGNORE NULLS clause in LAST_VALUE function.

20 has been returned because the LAST_VALUE function will return the FIRST NON NULL value if a NULL value is encountered at last while using IGNORE NULLS clause.


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