SQL, or Structured Query Language, provides a variety of functions to manipulate and retrieve data from databases. One such function is LAST_VALUE, which allows you to access the last value in a specified column within a partition.

The syntax for using LAST_VALUE in SQL is as follows:

LAST_VALUE(column_name) OVER (PARTITION BY partition_expression ORDER BY sort_expression [ROWS row_or_range_frame])

Let’s break down the different parts of the syntax:

• column_name: This is the name of the column from which you want to retrieve the last value.
• PARTITION BY: This clause is optional and allows you to specify the column or expression by which you want to partition the result set.
• partition_expression: This is the column or expression used for partitioning the data. The result set is divided based on the unique values of this expression.
• ORDER BY: This clause is mandatory and is used to specify the column or expression used for sorting the data within each partition.
• sort_expression: This is the column or expression used to order the data within each partition. The last value will be determined based on this ordering.
• ROWS: This clause is optional and is used to define a frame within which the function should operate.
• row_or_range_frame: This specifies the number of rows or a range of rows within the partition to consider for calculating the last value.

Here is an example that demonstrates the usage of LAST_VALUE:

SELECT employee_id, last_name, hire_date, LAST_VALUE(hire_date) OVER (ORDER BY hire_date) AS last_hire_date
FROM employees;

In this example, the LAST_VALUE function is used to retrieve the last hire date for each employee from the employees table. The result set will include the employee ID, last name, hire date, and the last hire date as a separate column.

Using LAST_VALUE can be helpful in scenarios where you need to access the most recent value in a column or find the latest records within each partition.

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