MySQL从表中引用自己的ID

Question

I have a table with two id columns and a name column the first of the id columns is the primary key, the second either refers to a primary key or is NULL.

+--+-----+----+
|id|subid|name|
+--+-----+----+
|1 |NULL |Tom |
+--+-----+----+
|2 |1    |Will|
+--+-----+----+

Given a name, I would like to, using only one SQL statement to output all entries with that given name, but if the secondary id field refers to a primary key, to output that entry instead.

Using the above example if I input "Tom" I would like to output name = "Tom" and if I input "Will" I would like to output name = "Tom" too?

Is that achievable with one SQL statement only, because I would like to avoid looping through results.

Answer 1

Yes. You want to use a join for this and an expression in the select :

select t.*
from table t left outer join
     table sub
     on t.subid = sub.id
where 'Tom' = t.name or 'Tom' = sub.name;