# SQL Sequence Group Aggregate Var and Dev Functions

> The `seq_group_agg_var()` and `seq_group_agg_dev()` functions compute the variance and standard deviation for the groups determined by the `group_by` argument.

> Following is an example script demonstrating the `seq_group_agg_var()` and `seq_group_agg_dev()` functions:

>         SELECT symbol,
>             seq_search(day, 20130101, 20130131) as Jan_13,
>             seq_group_agg_var(volume@Jan_13, Jan_13/7) as "week_var",
>             seq_group_agg_dev(volume@Jan_13, Jan_13/7) as "week_dev"
>         FROM Quote WHERE symbol = 'SYM0';

>         symbol
>         Jan_13{}
>         week_var{}
>         week_dev{}
>         ------------------------------------------------------------------------------
>         SYM0
>         {20130101, 20130104, 20130106, 20130110, 20130123, 20130125, 20130129}
>         {0.000000, 145542.250000, 0.000000, 0.000000, 143262.250000}
>         {0.000000, 381.500000, 0.000000, 0.000000, 378.500000}

> The following table illustrates how the first and last values correspond to the 5 groups (weeks):

> Volume_Jan_13 | var | dev | Week
> --- | --- | --- | ---
> 335 | 0.000000 | 0.000000 | 1
> 808 | 145542.250000 | 381.500000 | 2
> 45 |  |  | 2
> 402 | 0.000000 | 0.000000 | 3
> 732 | 0.000000 | 0.000000 | 4
> 48 | 143262.250000 | 378.500000 | 5
> 805 |  |  | 5

> Note that the huge variance and standard deviation values for weeks 2 and 5 indicate the great difference between the volume for the two trade dates in that week:

> `week 2: {808,45} -> 145542.25, 381.5`

> `week 5: {48,805} -> 143262.25, 378.5`

> ## 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:

>         g 6