Grouping consecutive rows with same value?

Question

Hi
I have a table in which three columns are:
ROWID  SHOPNAME
1      SHOP_C     
2      SHOP_A     
3      SHOP_C     
4      SHOP_C     
5      SHOP_A     
6      SHOP_A     
7      SHOP_C     
8      SHOP_B     
9      SHOP_B     
10     SHOP_E    
11     SHOP_A     
12     SHOP_D     
13     SHOP_D     
14     SHOP_F     
15     SHOP_G     
16     SHOP_F     
17     SHOP_C     
18     SHOP_C     
19     SHOP_C     
20     SHOP_C      Rowid is a primary key column with unique ids
Shopname is varchar2 column
I want to make groupings of every "shopname" value "order by ROWID" such that when there are consecutive rows of same shopname the group remains same and as soon as there is different value in shopname column for the next row the "group" changes.
below is my desired output is with 3rd column of groupings as follows:
ROWID  SHOPNAME    Groups
1      SHOP_C      1
2      SHOP_A      2
3      SHOP_C      3 ------> same grouping because Shop name is same
4      SHOP_C      3 ------> same grouping because shop name is same
5      SHOP_A      4 ----> different shopname so group changed.
6      SHOP_A      4 ----> same group as above because shopname is same
7      SHOP_C      5
8      SHOP_B      6
9      SHOP_B      6
10     SHOP_E      7
11     SHOP_A      8
12     SHOP_D      9
13     SHOP_D      9
14     SHOP_F      10
15     SHOP_G      11
16     SHOP_F      12
17     SHOP_C      13
18     SHOP_C      13
19     SHOP_C      13
20     SHOP_C      13I want that to be done via analytics, so that I can partition by clause for different shops over different cities
regards
Ramis.

Answer 1

with data(row_id, shop) as
select 1,      'SHOP_C' from dual union all
select 2,      'SHOP_A' from dual union all     
select 3,      'SHOP_C' from dual union all
select 4,      'SHOP_C' from dual union all    
select 5,      'SHOP_A' from dual union all     
select 6,      'SHOP_A' from dual union all
select 7,      'SHOP_C' from dual union all
select 8,      'SHOP_B' from dual union all
select 9,      'SHOP_B' from dual union all
select 10,     'SHOP_E' from dual union all
select 11,     'SHOP_A' from dual union all
select 12,     'SHOP_D' from dual union all
select 13,     'SHOP_D' from dual union all
select 14,     'SHOP_F' from dual union all
select 15,     'SHOP_G' from dual union all
select 16,     'SHOP_F' from dual union all
select 17,     'SHOP_C' from dual union all
select 18,     'SHOP_C' from dual union all
select 19,     'SHOP_C' from dual union all
select 20,     'SHOP_C' from dual
get_data as
  select row_id, shop,
         lag(shop) over (order by row_id) prev_shop
    from data
select row_id, shop,
       sum(case when shop = prev_shop
                  then  0
                  else 1
                  end
            ) over (order by row_id) grps
  from get_data;
ROW_ID SHOP   GRPS
     1 SHOP_C    1
     2 SHOP_A    2
     3 SHOP_C    3
     4 SHOP_C    3
     5 SHOP_A    4
     6 SHOP_A    4
     7 SHOP_C    5
     8 SHOP_B    6
     9 SHOP_B    6
    10 SHOP_E    7
    11 SHOP_A    8
    12 SHOP_D    9
    13 SHOP_D    9
    14 SHOP_F   10
    15 SHOP_G   11
    16 SHOP_F   12
    17 SHOP_C   13
    18 SHOP_C   13
    19 SHOP_C   13
    20 SHOP_C   13
20 rows selected