Apex. How to output NULL values too? - sql

Question

I had a question with a single sql query related to an interactive table in apex
Here, look, I prescribe a request in which I print all the existing artists in the database, but I only have entries where all the fields have values, and those in which at least one NULL are not displayed
select artist.name as "Artist", country.name as "Country" , city.name as "City of foundation", label.name as "Label of records"
from artist, country, city, label
where artist.country = country_id
and artist.city = city_id
and city.country = country_id
and artist.label = label_id
How to fix it?
https://i.stack.imgur.com/ZRYzm.png

Answer 1

As you didn't provide test case (a screenshot isn't quite enough - at least, not to me), I'll try to show what might be going on using Scott's schema.
There are 4 departments: note department 40, and the fact that nobody works in it:
SQL> select * from dept;
DEPTNO DNAME LOC
---------- -------------- -------------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
SQL> select * from emp where deptno = 40;
no rows selected
If you want to display all 4 departments and employees who work in them, you'd join EMP and DEPT table. Outer join lets you display department 40 (which, as we saw, has no employees):
SQL> select d.deptno, d.dname, e.ename
2 from dept d left join emp e on e.deptno = d.deptno --> outer join is here
3 order by d.deptno;
DEPTNO DNAME ENAME
---------- -------------- ----------
10 ACCOUNTING CLARK
10 ACCOUNTING MILLER
10 ACCOUNTING KING
20 RESEARCH JONES
20 RESEARCH SMITH
20 RESEARCH SCOTT
20 RESEARCH FORD
20 RESEARCH ADAMS
30 SALES WARD
30 SALES TURNER
30 SALES ALLEN
30 SALES JAMES
30 SALES MARTIN
30 SALES BLAKE
40 OPERATIONS --> this is what you're looking for
15 rows selected.
SQL>
You'd get the same result using the old Oracle's (+) outer join operator. You'd rather switch to modern joins and avoid that operator, though.
SQL> select d.deptno, d.dname, e.ename
2 from dept d, emp e
3 where d.deptno = e.deptno (+) --> the old outer join operator
4 order by d.deptno;
DEPTNO DNAME ENAME
---------- -------------- ----------
10 ACCOUNTING CLARK
10 ACCOUNTING MILLER
10 ACCOUNTING KING
20 RESEARCH JONES
20 RESEARCH SMITH
20 RESEARCH SCOTT
20 RESEARCH FORD
20 RESEARCH ADAMS
30 SALES WARD
30 SALES TURNER
30 SALES ALLEN
30 SALES JAMES
30 SALES MARTIN
30 SALES BLAKE
40 OPERATIONS
15 rows selected.
SQL>