String concatenation with GROUP BY - sql

Question

Using Postgres, I want to convert the following records:
ID serviceaccess
11 Value1
11 Value2
11 Value3
22 Value2
22 Value1
22 Value1
Into this result:
ID
11 value1, value2, value3
22 value2, value1, value1
I can't use functions, because the system I am using doesn't support those.
I could do case statements though.
I also checked the following:
SQL Server : GROUP BY clause to get comma-separated values
I tried this, but it doesn't work:
WITH RecurRanked ( dbid, rnk, serviceaccess)
AS (
SELECT t.t1.dbid, t.t1.rnk, t.t2.serviceaccess || ', ' || t.t1.serviceaccess
FROM t.t1
INNER JOIN t.t2 ON t.t1.dbid = RecurRanked.dbid AND t.t1.rnk = RecurRanked.rnk + 1)
SELECT dbid, MAX(serviceaccess)
FROM RecurRanked
GROUP BY dbid;
SELECT t.t1.dbid, t.t1.rnk, t.t2.serviceaccess || ', ' || t.t1.serviceaccess
FROM t.t1
INNER JOIN t.t2 ON t.t1.dbid = t.t2.dbid AND t.t1.rnk = t.t2.rnk + 1

Answer 1

I don't fully understand what you mean by "But I can't use functions, because the system, I am using doesn't support those. I am using postgres SQL though".
You can use the string_agg aggregate function in PostgreSQL.
select ID, string_agg(serviceaccess, ',') group by ID;

Answer 2

It's really hard to do what you want using pure SQL. It could be useful the following (which is not the perfect solution):
(e.g.) to convert the following records:
id| serviceaccess
-----------------------
11|" "
11|"Value1"
11|"Value2"
22|" "
22|"Value1"
22|"Value2"
22|"Value3"
Tested in postgresql. Unfortunately it can not be supported on the DBMS you are using:
SELECT t1.id, (max( t1.serviceaccess || ',') ||
max( t2.serviceaccess || ',') ||
max( t3.serviceaccess || ',') ||
max( t4.serviceaccess || ',') ||
max( t5.serviceaccess)) as Services
FROM test as t1
INNER JOIN test as t2 ON t1.id =t2.id AND (t2.serviceaccess > t1.serviceaccess or
t1.serviceaccess = ' ')
INNER JOIN test as t3 ON t2.id =t3.id AND (t3.serviceaccess > t2.serviceaccess or
t2.serviceaccess = ' ')
INNER JOIN test as t4 ON t3.id =t4.id AND (t4.serviceaccess > t3.serviceaccess or
t3.serviceaccess = ' ')
INNER JOIN test as t5 ON t4.id =t5.id AND (t5.serviceaccess > t4.serviceaccess or
t4.serviceaccess = ' ')
GROUP BY t1.id
Result:
id| services
------------------------------
22| " , ,Value1,Value2,Value3"
11| " , , ,Value1,Value2"
kind regards!