concatenate all rows

[simply_dba]

select min(col1) from t1

This does not guarantee the first row.How about this?

select col1 from t1 where rownum=1

[Bonker]

Originally posted by simply_dba This does not guarantee the first row.How about this? select col1 from t1 where rownum=1

In database there is no concept of first row, last row etc... If you are inserting records with timestamp or with sequence only then you can get the first row inserted or last row inserted.

In 8k blocksize database try this

create table test (a char(2000), b char(2000), c char(2000), d char(2000));

insert into test values ('1','b','c','d');
insert into test values ('2','b','c','d');
insert into test values ('3','b','c','d');

select a from test where rownum=1; -- what is value of a shown by this query?

delete from test where a='1';

commit;

insert into test values ('4','b','c','d');

select a from test where rownum=1; -- what is value of a now shown by this query?

[simply_dba]

Yes, but the statement is more likely to fetch the answer the original poster wanted than using min()

[John Spencer]

Yes, but the statement is more likely to fetch the answer the original poster wanted than using min()

WHERE ROWNUM = 1 means get me one random row from the query. The row returned can and will change for any number of reasons. Bonker demonstrated one way (delete/insert), changing access paths is another (e.g. Oracle decides to use an index instead of a full scan). Another reason would be simply order of insertion.

SQL> CREATE TABLE t (col1 VARCHAR2(1));
 
Table created.
  
SQL> INSERT INTO t VALUES ('e');
 
1 row created.
 
SQL> INSERT INTO t VALUES ('d');
 
1 row created.
 
SQL> INSERT INTO t VALUES ('c');
 
1 row created.
 
SQL> INSERT INTO t VALUES ('b');
 
1 row created.
 
SQL> INSERT INTO t VALUES ('a');
 
1 row created.
 
SQL> COMMIT;
 
Commit complete.

SQL> SELECT REPLACE(col1, ' ')
  2  FROM (SELECT SYS_CONNECT_BY_PATH(col1,' ') col1, level
  3        FROM t
  4        START WITH col1 = (SELECT MIN(col1) FROM t)
  5        CONNECT BY PRIOR col1 < col1
  6        ORDER BY level DESC)
  7        WHERE rownum = 1;
 
REPLACE(COL1,'')
-----------------
abcde
 
SQL> SELECT REPLACE(col1, ' ')
  2  FROM (SELECT SYS_CONNECT_BY_PATH(col1,' ') col1, level
  3        FROM t
  4        START WITH col1 = (SELECT col1 FROM t WHERE rownum = 1)
  5        CONNECT BY PRIOR col1 < col1
  6        ORDER BY level DESC)
  7        WHERE rownum = 1
 
REPLACE(COL1,'')
-----------------
e

So, which one is more likely to be correct?

TTFN
John

[kilroy]

I have the following table and data:

CREATE TABLE t1 (col1 VARCHAR2(1), col2 VARCHAR2(25));
INSERT INTO t1 (col1,col2) VALUES ('1','TEST1');
INSERT INTO t1 (col1,col2) VALUES ('2','TEST1');
INSERT INTO t1 (col1,col2) VALUES ('5','TEST2');
INSERT INTO t1 (col1,col2) VALUES ('9','TEST2');
INSERT INTO t1 (col1,col2) VALUES ('1','TEST3');
INSERT INTO t1 (col1,col2) VALUES ('1','TEST4');
INSERT INTO t1 (col1,col2) VALUES ('5','TEST5');


I would like to get the following results from a single query:

co1 col2
TEST1 1,2
TEST2 5,9
TEST3 1
TEST4 1
TEST5 5


If anyone knows how to do this using connect by i would appreciate your help. Thanks