How do i calculate minimum and maximum for groups in a sequence in SQL Server? -


i having following data in database table in sql server:

id  date        val_a   val_b   val_c   avg     vector  minmaxpoints 329 2016-01-15  78.09   68.40   70.29   76.50   below   68.40 328 2016-01-14  79.79   75.40   76.65   76.67   below   75.40 327 2016-01-13  81.15   74.59   79.00   76.44   above   81.15 326 2016-01-12  81.95   77.04   78.95   76.04   above   81.95 325 2016-01-11  82.40   73.65   81.34   75.47   above   82.40 324 2016-01-08  78.75   73.40   77.20   74.47   above   78.75 323 2016-01-07  76.40   72.29   72.95   73.74   below   72.29 322 2016-01-06  81.25   77.70   78.34   73.12   above   81.25 321 2016-01-05  81.75   76.34   80.54   72.08   above   81.75 320 2016-01-04  80.95   75.15   76.29   70.86   above   80.95

the column mimmaxpoints should contain lowest of val_b until vector 'below' , highest of val_a until vector 'above'. so, have following values in minmaxpoints:

minmaxpoints 68.40 68.40 82.40 82.40 82.40 82.40 72.29 81.75 81.75 81.75

is possible without cursor?

any appreciated!.

at first apply classic gaps-and-islands determine groups (gaps/islands/above/below) , calculate min , max each group.

i assume id column defines order of rows.

tested on sql server 2008. here sql fiddle.

sample data

declare @t table ([id] int, [dt] date, [val_a] float, [val_b] float, [val_c] float, [avg] float,  [vector] varchar(5));  insert @t ([id], [dt], [val_a], [val_b], [val_c], [avg], [vector]) values (329, '2016-01-15', 78.09, 68.40, 70.29, 76.50, 'below'), (328, '2016-01-14', 79.79, 75.40, 76.65, 76.67, 'below'), (327, '2016-01-13', 81.15, 74.59, 79.00, 76.44, 'above'), (326, '2016-01-12', 81.95, 77.04, 78.95, 76.04, 'above'), (325, '2016-01-11', 82.40, 73.65, 81.34, 75.47, 'above'), (324, '2016-01-08', 78.75, 73.40, 77.20, 74.47, 'above'), (323, '2016-01-07', 76.40, 72.29, 72.95, 73.74, 'below'), (322, '2016-01-06', 81.25, 77.70, 78.34, 73.12, 'above'), (321, '2016-01-05', 81.75, 76.34, 80.54, 72.08, 'above'), (320, '2016-01-04', 80.95, 75.15, 76.29, 70.86, 'above');

query

to understand better how works examine results of each cte.

cte_rownumbers calculates 2 sequences of row numbers.

cte_groups assigns number each group (above/below).

cte_minmax calculates min/max each group.

final select picks min or max return.

with cte_rownumbers (     select [id], [dt], [val_a], [val_b], [val_c], [avg], [vector]         ,row_number() on (order id desc) rn1         ,row_number() on (partition vector order id desc) rn2     @t ) ,cte_groups (     select [id], [dt], [val_a], [val_b], [val_c], [avg], [vector]         ,rn1-rn2 groups     cte_rownumbers ) ,cte_minmax (     select [id], [dt], [val_a], [val_b], [val_c], [avg], [vector]         ,max(val_a) over(partition groups) maxa         ,min(val_b) over(partition groups) minb     cte_groups ) select [id], [dt], [val_a], [val_b], [val_c], [avg], [vector]     ,case          when [vector] = 'below' minb         when [vector] = 'above' maxa     end minmaxpoints cte_minmax order id desc;

result

+-----+------------+-------+-------+-------+-------+--------+--------------+ | id  |     dt     | val_a | val_b | val_c |  avg  | vector | minmaxpoints | +-----+------------+-------+-------+-------+-------+--------+--------------+ | 329 | 2016-01-15 | 78.09 | 68.4  | 70.29 | 76.5  | below  | 68.4         | | 328 | 2016-01-14 | 79.79 | 75.4  | 76.65 | 76.67 | below  | 68.4         | | 327 | 2016-01-13 | 81.15 | 74.59 | 79    | 76.44 | above  | 82.4         | | 326 | 2016-01-12 | 81.95 | 77.04 | 78.95 | 76.04 | above  | 82.4         | | 325 | 2016-01-11 | 82.4  | 73.65 | 81.34 | 75.47 | above  | 82.4         | | 324 | 2016-01-08 | 78.75 | 73.4  | 77.2  | 74.47 | above  | 82.4         | | 323 | 2016-01-07 | 76.4  | 72.29 | 72.95 | 73.74 | below  | 72.29        | | 322 | 2016-01-06 | 81.25 | 77.7  | 78.34 | 73.12 | above  | 81.75        | | 321 | 2016-01-05 | 81.75 | 76.34 | 80.54 | 72.08 | above  | 81.75        | | 320 | 2016-01-04 | 80.95 | 75.15 | 76.29 | 70.86 | above  | 81.75        | +-----+------------+-------+-------+-------+-------+--------+--------------+

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