Oracle sql - Invalid Identifier LISTAGG

Question

I'm new using the LISTAGG function. When I run the following script I get an invalid identifier error:

ORA-00904: "TE"."COUNTRY": invalid identifier

Any ideas why?

SELECT te.country, listagg(te.exception_date, ' ,') WITHIN GROUP (ORDER BY te.country) country
FROM 
(select unique te.exception_date, 
case when te.country is null then (select max(tt.country) from tt_transport tt where te.route = tt.route) else te.country end country
  from tt_exception te
  where trunc(te.exception_date) > '01-JAN-2015'
  and te.plant = 'Z'
  and not case when te.country is null then (select max(tt.country) from tt_transport tt where te.route = tt.route) else te.country end is null
  order by te.country) te
group by te.country
UNION ALL
SELECT te.country, listagg(te.exception_date, ' ,') WITHIN GROUP (ORDER BY te.country) country
FROM 
(select unique te.exception_date, 'GB' country
  from tt_exception te
  where trunc(te.exception_date) > '01-JAN-2015'
  and te.plant = 'W'
  and te.country is null
  order by te.country)
group by te.country

Answer 1

In the second part of the query, there is no alias defined for the inline view. You should name it and then refer to it.

SELECT te.country, listagg(te.exception_date, ' ,') WITHIN GROUP (ORDER BY te.country) country
FROM 
(select unique te.exception_date, 'GB' country
  from tt_exception te
  where trunc(te.exception_date) > '01-JAN-2015'
  and te.plant = 'W'
  and te.country is null
  order by te.country) te --missing alias
group by te.country

Or you can just refer to the column name without the alias.

SELECT country, listagg(exception_date, ' ,') WITHIN GROUP (ORDER BY country) country
    FROM 
    (select unique te.exception_date, 'GB' country
      from tt_exception te
      where trunc(te.exception_date) > '01-JAN-2015'
      and te.plant = 'W'
      and te.country is null
      order by te.country)
    group by country

Answer 2

SELECT te.country, listagg(te.exception_date, ' ,') WITHIN GROUP (ORDER BY te.country) country
FROM 
(select unique te.exception_date, 
case when te.country is null then (select max(tt.country) from tt_transport tt where te.route = tt.route) else te.country end country
  from tt_exception te
  where trunc(te.exception_date) > '01-JAN-2015'
  and te.plant = 'Z'
  and not case when te.country is null then (select max(tt.country) from tt_transport tt where te.route = tt.route) else te.country end is null
  order by te.country) te
group by te.country
UNION ALL
SELECT te.country, listagg(te.exception_date, ' ,') WITHIN GROUP (ORDER BY te.country) country
FROM 
(select unique te.exception_date, 'GB' country
  from tt_exception te
  where trunc(te.exception_date) > '01-JAN-2015'
  and te.plant = 'W'
  and te.country is null
  order by te.country)--**you are missing the alias "te"**
group by te.country