How to group by on consecutive values in SQL

Question

I have a table in SQL Server 2014 with sample data as follows.

WK_NUM | NET_SPRD_LCL 
10       0 
11       1500 
12       3600 
13       3800 
14       4000

Answer 1

Assuming you mean consecutive line 1, 2, 3, 4, 5 ... etc. and NOT 1, 3, 5, 8, 12, etc.

then, if you don't need to know which pair of consecutive records it was:

Select case when exists
   (Select * from table f
       join table n
          on n.Wk_Num = f.Wk_Num + 1
             and n.NET_SPRD_LCL > 3500
             and f.NET_SPRD_LCL > 3500
             and n.Wk_Num < 27
    then 2000 else null end

If you do need to identify the pair of records, then:

Select f.wk_Num firstWorkNbr, f.NET_SPRD_LCL firstNetSpread,
       n.wk_Num nextWorkNbr, n.NET_SPRD_LCL nextNetSpread
from table f
   join table n
       on n.Wk_Num = f.Wk_Num + 1
         and n.NET_SPRD_LCL > 3500
         and f.NET_SPRD_LCL > 3500
          and n.Wk_Num < 27
 Where not exists 
    (Select * from table f0
       join table n0 
           on n0.Wk_Num = f0.wk_Num + 1
              and n0.WkNum < f.Wk_Num))

on the other hand if the consecutive is simply increasing, then it's a bit harder. You need to use a subquery to determine the next consecutive record...

Select case when exists
   (Select * from table f
       join table n
          on n.Wk_Num = (Select Min(Wk_Num) from table
                         Where Wk_Num > f.Wk_Num)
             and n.NET_SPRD_LCL > 3500
             and f.NET_SPRD_LCL > 3500
             and n.Wk_Num < 27
    then 2000 else null end

and if you need to fetch the data for the specific first pair of records that qualify (the 2000 at the end is unnecessary since if there is no qualifying pair nothing will be returned.)

Select f.wk_Num firstWorkNbr, f.NET_SPRD_LCL firstNetSpread,
       n.wk_Num nextWorkNbr, n.NET_SPRD_LCL nextNetSpread, 2000 outValue
from table f
   join table n
       on n.Wk_Num = (Select Min(Wk_Num) from table
                      Where Wk_Num > f.Wk_Num)
         and n.NET_SPRD_LCL > 3500
         and f.NET_SPRD_LCL > 3500
          and n.Wk_Num < 27
 Where not exists 
    (Select * from table f0
       join table n0 
           on n0.Wk_Num = (Select Min(Wk_Num) from table
                           Where Wk_Num > f0.Wk_Num)
              and n0.WkNum < f.Wk_Num))