concatenation - 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

RES3

now I want to have a result like the following one:

FOOCONCAT
-----
RES1RES2RES3

Are there any ways to do this in sql?

Answer 1

In SQL Server:

SELECT  col1 AS [text()]
FROM    foo
FOR XML PATH ('')

In MySQL:

SELECT  GROUP_CONCAT(col1 SEPARATOR '')
FROM    foo

In PostgreSQL:

SELECT  array_to_string
        (
        ARRAY
        (
        SELECT  col1
        FROM    foo
        ), ''
        )

In Oracle:

SELECT  *
FROM    (
        SELECT  col1, ROW_NUMBER() OVER(ORDER BY 1) AS rn
        FROM    foo
        MODEL
        DIMENSION BY
                (rn)
        MEASURES
                (col1, col1 AS group_concat, 0 AS mark)
        RULES UPDATE (
                group_concat[rn > 1] =  group_concat[CV() - 1] || col1[CV()],
                mark[ANY] = PRESENTV(mark[CV() + 1], 0, 1)
                )
        )
WHERE   mark = 1