I currently am working on a project within Crystal Reports that refuses to use the undocumented function WM_CONCAT, which is allowable within Oracle 10g. Here is the WM_CONCAT header information
WM_CONCAT(p1 IN VARCHAR2) RETURN VARCHAR2
To use WM_CONCAT I pass it the following: WM_CONCAT(column1); This function seems to accept a column of type varchar2, and returns a comma delimited list of values from the column. I currently have a custom version of this function that works (on my work computer), but it is not optimal and lacks re-usability. Could anyone provide a good, re-usable function like WM_CONCAT that I could use?
Do you get an error message when you use wm_concat? Unlike functions like to_char, it is owned by wmsys and you might need to use wmsys.wm_concat to use it. (unless you create the necessary synonyms of course).
Now for the actual question,
This technique is called string aggregation.
You could find a lot of other alternatives here.
http://www.oracle-base.com/articles/10g/StringAggregationTechniques.php For other methods, Search for "stragg" on http://asktom.oracle.com Another useful link : http://www.orafaq.com/node/2290
This is probably the most used one. A lot of teams write their own custom functions which more or less do the same.
CREATE OR REPLACE FUNCTION get_employees (p_deptno in emp.deptno%TYPE)
RETURN VARCHAR2
IS
l_text VARCHAR2(32767) := NULL;
BEGIN
FOR cur_rec IN (SELECT ename FROM emp WHERE deptno = p_deptno) LOOP
l_text := l_text || ',' || cur_rec.ename;
END LOOP;
RETURN LTRIM(l_text, ',');
END;
/
SHOW ERRORS
while this solution works for varchar2 and number, the best generic solution can be built using Oracle ODCIAggregate interface.
http://download-west.oracle.com/docs/cd/B14117_01/appdev.101/b10800/dciaggfns.htm#sthref462
Implementation for the same is at the first link above at www.oracle-base.com