Question

I’m hoping to return a single row with a comma separated list of values from a query that returns multiple rows in Oracle, essentially flattening the returned rows into a single row.

In PostgreSQL this can be achieved using the array and array_to_string functions like this:

Given the table “people”:

id | name
---------
1  | bob
2  | alice
3  | jon

The SQL:

select array_to_string(array(select name from people), ',') as names;

Will return:

names
-------------
bob,alice,jon

How would I achieve the same result in Oracle 9i?

Thanks,

Matt

Answer 1

Tim Hall has the definitive collection of string aggregation techniques in Oracle.

If you’re stuck on 9i, my personal preference would be to define a custom aggregate (there is an implementation of string_agg on that page) such that you would have

SELECT string_agg( name )
  FROM people

But you have to define a new STRING_AGG function. If you need to avoid creating new objects, there are other approaches but in 9i they’re going to be messier than the PostgreSQL syntax.