PL/SQL LEAD function is a powerful analytic function in the Oracle database that is used to access data from the subsequent row in a table or result set. The LEAD function allows you to retrieve the value of a column from the next row based on the current row. This function is commonly used in data analysis and reporting scenarios to compute values across a dataset.
The syntax of the LEAD function in Oracle is as follows:
LEAD(column, offset, default_value) OVER (ORDER BY column ASC/DESC)
The parameters of the LEAD function are:
column: This is the column name or expression whose value you want to retrieve from the subsequent row.
offset: This is the number of rows to look ahead to retrieve the value. The default value is 1.
default_value: This is the value returned when there is no subsequent row to retrieve a value from. The default value is NULL.
ORDER BY: This is the column or columns used to sort the result set in ascending or descending order.
Here’s an example of using the LEAD function in a query:
SELECT employee_id, salary, LEAD(salary) OVER (ORDER BY salary DESC) as next_salary FROM employees;
In this example, the LEAD function is used to retrieve the salary of the next employee based on the current row’s salary. The function is applied to the “salary” column, and the “ORDER BY” clause is used to sort the result set in descending order by the “salary” column. The result set will display the employee_id, salary, and next_salary values.
The PL/SQL LEAD function can also be used in conjunction with other analytic functions like SUM, AVG, MIN, MAX, etc., to calculate complex results based on the dataset. With the LEAD function, you can easily access and analyze data from subsequent rows in a table or result set, making it an essential tool for data analysis and reporting in the Oracle database.