Sql group by query and concatenation

Question

Hi folks,
I have question.I need to concatenate the columns like this.
i/p
i_txt txt
1000 abc
1000 def
1001 things
1001 to
1001 do
1002 is
1002 it
1002 possible
O/P should be like this
i_txt txt
1000 abcdef
1001 things to do
1002 is it possible
Thanks in advance
Raj

Answer 1

Tubby's provided the useful search term: String Aggregation.
Assuming you've studied Tim's article, you now know that the approach and techniques you can use are database-version dependant.
So, please: always mention your database-version when posting a question.
Now, when looking at your desired output, it looks like a simple string aggregation question, however:
You don't seem to want 'abcdef' connected by a space?
Without knowing why, you can use case and replace the space for that specific i_txt.
But, that requires some hard-coding:
SQL> select * from t;
     I_TXT TXT
      1000 abc
      1000 def
      1001 things
      1001 to
      1001 do
      1002 is
      1002 it
      1002 possible
8 rows selected.
SQL> select i_txt
  2  ,      ltrim(sys_connect_by_path(txt, ' '), ' ') txt
  3  from ( select i_txt
  4         ,      txt
  5         ,      row_number() over (partition by i_txt order by i_txt ) rn
  6         from t
  7       )
  8  where connect_by_isleaf=1    
  9  start with rn=1
10  connect by i_txt = prior i_txt
11         and rn = prior rn+1;
     I_TXT TXT
      1000 abc def
      1001 things to do
      1002 is it possible
3 rows selected.
SQL> select i_txt
  2  ,      case i_txt
  3           when 1000
  4           then  replace(sys_connect_by_path(txt, ' '), ' ')
  5           else  ltrim(sys_connect_by_path(txt, ' '), ' ')
  6         end txt
  7  from ( select i_txt
  8         ,      txt
  9         ,      row_number() over (partition by i_txt order by i_txt ) rn
10         from t
11       )
12  where connect_by_isleaf=1    
13  start with rn=1
14  connect by i_txt = prior i_txt
15         and rn = prior rn+1;
     I_TXT TXT
      1000 abcdef
      1001 things to do
      1002 is it possible
3 rows selected. This example works when you're on database version 10G and onwards.
Perhaps we could find other ways, if you can explain when you do and do not want your strings aggregated/concatenated by a space