Concat all column values in sql

Question

How to concat all column values from differenct rows returned from a sql query into one value? This is an example:

a query returns:

FOO
------
RES1

RES2
         


        

Answer 1

Here is the answer you are looking for; I had a feeling the solution lay in the CONNECT BY operation, I just hadn't used the SYS_CONNECT_BY_PATH pseudocolumn before (which displays the full path to the node in a tree, separating node names by a "/"). Assuming that your set of "foo" values before are multiple rows in a table, grouped by a column "myKey", e.g.:

myKey    foo
-------- ----------
group 1  apple
group 1  orange
group 1  pear
group 2  ape
group 2  bear
group 2  kitten

you can treat the data as if it were a tree schema, and pretend that the values of each group represent nodes going down a branch. In that case, you'd do this:

  SELECT myKey
       , SUBSTR(MAX(REPLACE(SYS_CONNECT_BY_PATH(foo, '/')
                           ,'/'
                           ,' '
                           )
                   )
               ,2
               ) FooConcat
    FROM ( SELECT MyKey
                , Foo
                , row_number() OVER (Partition by myKey order by myKey) NodeDepth
             FROM MyTable
         )
   START WITH NodeDepth = 1
 CONNECT BY PRIOR myKey = myKey
     AND PRIOR NodeDepth = NodeDepth -1
GROUP BY myKey
;

Of course, the order of the concatenated values would be random; if your table had another column ("bar") that you could use as an ordering field that was ascending and contiguous, you could dispense with the subquery (which only exists to put an imaginary depth to the tree) and use the table directly, replacing NodeDepth with bar.

Answer 2

select cast(res1 as varchar)+cast(res2 as varchar)+cast(res3 as varchar) as fooconcat from foo

If the columns are already strings you do not need the cast, you can just do:

select res1 + res2 + res3  as fooconcat from foo

For data from multiple rows, use PIVOT.

Answer 3

It might not be what you're looking for, but I've had good luck in the past with constructions like this:

SELECT      MAX(DECODE(fookey, 1, foo, NULL))
         || MAX(DECODE(fookey, 2, foo, NULL))
         || MAX(DECODE(fookey, 3, foo, NULL))
         || MAX(DECODE(fookey, 4, foo, NULL))
       , groupingvalue
    FROM mytable
GROUP BY groupingvalue;

It's platform independent, and it works well when you have a arbitrary, but limited number of values for foo, and they're based on some other key value. For example, if you have a table of invoices, and you want to see all the line times from the invoice on a single row, concatenated, and you have an upper limit of 5 line items, it would look like this:

SELECT      MAX(DECODE(lineno, 1, foo, NULL))
         || ', '
         || MAX(DECODE(lineno, 2, foo, NULL))
         || ', '
         || MAX(DECODE(lineno, 3, foo, NULL))
         || ', '
         || MAX(DECODE(lineno, 4, foo, NULL))
         || ', '
         || MAX(DECODE(lineno, 5, foo, NULL))
       , invoiceid
    FROM lineitem
GROUP BY invoiceid;

Answer 4

The mysql way:

select group_concat(somecolumn separator '') from sometable

Answer 5

Edit: Since version 8.4.0 CUBRID provides 90% compatibility with MySQL. Thus, it supports GROUP_CONCAT which has similar syntax as in MySQL:

CREATE TABLE t(i int);
INSERT INTO t VALUES (4),(2),(3),(6),(1),(5);

SELECT GROUP_CONCAT(i*2+1 ORDER BY 1 SEPARATOR '') FROM t;

group_concat(i*2+1 order by 1 separator '')
======================
  '35791113'

Quite powerful, isn't it? And below is an alternative solution supported natively in CUBRID.

SELECT MAX(SYS_CONNECT_BY_PATH(s_name, '')) AS conc_s_name
FROM (
     SELECT ROWNUM AS r, s_name FROM code
) AS res
START WITH r = 1
CONNECT BY PRIOR r = r - 1;

It's so interesting that this way of concatenating different row column values in CUBRID is almost identical to Oracle's way as provided by @devio. In CUBRID it looks a little bit easier though.

Answer 6

Concatenating strings depends on the database you are using (you havnt mentioned what version in your question so here goes)...

In Oracle and DB2 you can use the CONCAT function... CONCAT(string, string)

SQL Server you can use the '+' operator... string1 + string2 + string3

In MySQL it is CONCAT(string, string... n_string)

Finally in PostgreSQL it is TEXTCAT(string, string)...

...I got this out of this little cool book I have sitting on my desk SQL Pocket Guide from O'Reilly... check it out!

:)