Você pode fazer isso usando ROW_NUMBER função analítica. Consulte Encontra um intervalo de valores consecutivos em uma sequência de números ou datas .
Por exemplo,
Intervalo
SQL> with data(num) as(
2 select 1 from dual union
3 select 2 from dual union
4 select 3 from dual union
5 select 5 from dual union
6 select 6 from dual union
7 select 7 from dual union
8 select 10 from dual union
9 select 11 from dual union
10 select 12 from dual union
11 select 20 from dual
12 )
13 select min(num)||'-'|| max(num) as "range"
14 from (select num,
15 num-Row_Number() over(order by num)
16 as rn
17 from data)
18 group by rn
19 order by min(num);
range
-------------------------------------------------
1-3
5-7
10-12
20-20
SQL>
Lista
SQL> with data(num) as(
2 select 1 from dual union
3 select 2 from dual union
4 select 3 from dual union
5 select 5 from dual union
6 select 6 from dual union
7 select 7 from dual union
8 select 10 from dual union
9 select 11 from dual union
10 select 12 from dual union
11 select 20 from dual
12 )
13 SELECT listagg(range, ',') WITHIN GROUP(
14 ORDER BY min_num) AS "list"
15 FROM
16 (SELECT MIN(num) min_num,
17 MIN(num)
18 ||'-'
19 || MAX(num) range
20 FROM
21 (SELECT num, num-Row_Number() over(order by num) AS rn FROM DATA
22 )
23 GROUP BY rn
24 );
list
-------------------------------------------------------------------------
1-3,5-7,10-12,20-20
SQL>
Atualizar O OP quer uma solução em PL/SQL para armazenar a lista em uma variável PL/SQL.
Configuração
SQL> CREATE TABLE t AS
2 SELECT *
3 FROM
4 ( WITH data(num) AS
5 ( SELECT 1 FROM dual
6 UNION
7 SELECT 2 FROM dual
8 UNION
9 SELECT 3 FROM dual
10 UNION
11 SELECT 5 FROM dual
12 UNION
13 SELECT 6 FROM dual
14 UNION
15 SELECT 7 FROM dual
16 UNION
17 SELECT 10 FROM dual
18 UNION
19 SELECT 11 FROM dual
20 UNION
21 SELECT 12 FROM dual
22 UNION
23 SELECT 20 FROM dual
24 )
25 SELECT * FROM DATA);
Table created.
Bloco PL/SQL
SQL> SET SERVEROUTPUT ON
SQL> DECLARE
2 v_list VARCHAR2(100);
3 BEGIN
4 SELECT listagg(RANGE, ',') WITHIN GROUP(
5 ORDER BY min_num)
6 INTO v_list
7 FROM
8 (SELECT MIN(num) min_num,
9 MIN(num)
10 ||'-'
11 || MAX(num) range
12 FROM
13 (SELECT num, num-Row_Number() over(order by num) AS rn FROM t
14 )
15 GROUP BY rn
16 );
17 dbms_output.put_line(v_list);
18 END;
19 /
1-3,5-7,10-12,20-20
PL/SQL procedure successfully completed.
SQL>
