Stuck at inserting records into MariaDB conditionally

Question

I know about insert ignore. That's of no use, because MariaDB does not consider NULL to be part of the uniqude index.

Therefore I have to use if ... else.

But this code does not run:

select *
from Nodes 
where `Key` = 'FAQPage';

if not found_row() then
   insert into Nodes (`Key`, ParentId)
   values ('FAQPage', null)
end if;

How can I use if ... else to conditionally insert data in MariaDB?

Answer 1

INSERT INTO Nodes (`Key`, ParentId)
SELECT @key, @parentid
WHERE NOT EXISTS ( SELECT NULL
                   FROM Nodes
                   WHERE `Key` <=> @key
                     AND ParentId <=> @parentid )

@key and @parentid are placeholders for the values to be inserted.

So if the row with the values to be inserted already exists then the subquery detects this, and none rows is inserted.