Is there an Oracle SQL query that aggregates multiple rows into one row? [duplicate]

Solution 1:

(WARNING - WM_CONCAT is an unsupported function that was removed in version 12c. Unless you're using a very old database, you should avoid this function. You should probably use LISTAGG instead.)

It depends on the version of Oracle you're using. If it supports the wm_concat() function, then you can simply do something like this:

SELECT field1, wm_concat(field2) FROM YourTable GROUP BY field2;

wm_concat() basically works just like group_concat() in MySQL. It may not be documented, so fire up ye olde sqlplus and see if it's there.

If it isn't there, then you'll want to implement something equivalent yourself. You can find some instructions on how to do this in the string aggregation page at oracle-base.com.

Solution 2:

Pretty old topic, but it could help others since Oracle improved in the mean time.

The LISTAGG function is what you are looking for (in 11g at least)

Solution 3:

In Oracle 10g+:

SELECT  *
FROM    (
        SELECT  *
        FROM    mytable
        MODEL
        PARTITION BY
                (grouper)
        DIMENSION BY
                (ROW_NUMBER() OVER (PARTITION BY grouper ORDER BY id) AS rn)
        MEASURES
                (val, val AS group_concat, 0 AS mark)
        RULES SEQUENTIAL ORDER (
                group_concat[rn > 1] ORDER BY rn = group_concat[CV() - 1] || ', ' || val[CV()],
                mark[ANY] ORDER BY rn = PRESENTV(mark[CV() + 1], 0, 1)
                )
        )
WHERE   mark = 1
ORDER BY
        grouper

See this article in my blog for explanations:

• GROUP_CONCAT in Oracle 10g

Solution 4:

Try something like :

SELECT
    field1,
    RTRIM(REPLACE(REPLACE(XMLAgg(XMLElement("x", field2) ORDER BY field2), '<x>'), '</x>', ' ')) AS field2s
  FROM yourTable
  GROUP BY field1

Freely inspired by an answer found in this Oracle forum.

EDIT: this solution proved very resources intensive with requests involving something like 10⁵ rows. I ended up replacing this by custom aggregate functions as suggested by John.