# SQL Sequence Diff Function

> The `seq_diff()` function returns a sequence of values representing the difference of element n minus element n-1.

> Following is an example script demonstrating the `seq_diff()` function:

>         INSERT INTO SimpleSequence(testNumber,iVal1)
>         VALUES(2,'{4,9,2,9,1,4,9,7,5,3}');

>         SELECT iVal1, seq_diff(iVal1) AS "diff" FROM SimpleSequence WHERE testNumber = 2;

>         iVal1{}
>         diff{}
>         ----------------------------------------------------------------------
>         {4, 9, 2, 9, 1, 4, 9, 7, 5, 3}
>         {0, 5, -7, 7, -8, 3, 5, -2, -2, -2}

> The elements in the result sequence are obtained as follows:

> n | n-1 | result
> --- | --- | ---
> 4 | - | 0
> 9 | 4 | 9 - 4 = 5
> 2 | 9 | 2 - 9 = -7
> 9 | 2 | 9 - 2 = 7
> 1 | 9 | 1 - 9 = -8
> 4 | 1 | 4 - 1 = 3
> 9 | 4 | 9 - 4 = 5
> 7 | 9 | 7 - 9 = -2
> 5 | 7 | 5 - 7 = -2
> 3 | 5 | 3 - 5 = -2

> (Note that the first element in the return sequence is just the place holder value of 0 since there is not n-1 value to compare it to.)

> ## Sample script

> A sample script to demonstrate this `select` statement using xSQL can be run from the `samples/xsql/scripts/financial` directory with the following command:

>         f 2