Window Function Descriptions +----------+------+------+------+----------+-----------+ In the example, the  LAG()  and  LEAD()  calls use the default  N  and  default  values of 1 and  NULL , respectively. The first row shows what happens when there is no previous row for  LAG() : The function returns the default  value (in this case,  NULL ). The last row shows the same thing when there is no next row for LEAD() . LAG()  and  LEAD()  also serve to compute sums rather than differences. Consider this data set, which contains the first few numbers of the Fibonacci series: mysql>  SELECT n FROM fib ORDER BY n; +------+ | n | +------+ | 1 | | 1 | | 2 | | 3 | | 5 | | 8 | +------+ mysql>  SELECT n, LAG(n, 1, 0) OVER w AS ’lag’, LEAD(n, 1, 0) OVER w AS ’lead’, n + LAG(n, 1, 0) OVER w AS ’next_n’, n + LEAD(n, 1, 0) OVER w AS ’next_next_n’ FROM fib WINDOW w AS (ORDER BY n); +------+------+------+--------+-------------+ | n | lag | lead | next_n | next_next_n | +------+------+------+--------+-------------+ | 1 | 0 | 1 | 1 | 2 | | 1 | 1 | 2 | 2 | 3 | | 2 | 1 | 3 | 3 | 5 | | 3 | 2 | 5 | 5 | 8 | | 5 | 3 | 8 | 8 | 13 | | 8 | 5 | 0 | 13 | 8 | +------+------+------+--------+-------------+ The following query shows the  LAG()  and  LEAD()  values for the rows adjacent to the current row. It also uses those functions to add to the current row value the values from the preceding and following rows. The effect is to generate the next number in the Fibonacci series, and the next number after that: One way to generate the initial set of Fibonacci numbers is to use a recursive common table expression. For an example, see Fibonacci Series Generation. Beginning with MySQL 8.0.22, you cannot use a negative value for the rows argument of this function. Returns the value of  expr  from the last row of the window frame. over_clause  is as described in Section 12.21.2, “Window Function Concepts and Syntax” . null_treatment  is as described in the section introduction. For an example, see the  FIRST_VALUE()  function description. • LAST_VALUE( expr )  [ null_treatment ]  over_clause 2421