> And columns in primary keys must be NOT NULL. Columns in unique
> keys can be NULL (if they are NOT NULL, then the unique key is
> functionally the same as a primary key).
OK, thanks guys for the explanation.
Then the result of mysqldump table definition part:
UNIQUE KEY HONstid (HONstid,HONname)
means that I have two unique keys:
and also the
This does not make too much sense; if I can have only one HONstid in my
table, then of course i can have only one kind of (HONstid,HONname)
combination. In the actual table, I have multiple occurences of values
(HONstid,HONname)in the HONstid column, i.e. it does not seem like
HONstid in itself was a unique key. Only the (HONstid,HONname)
combination is unique.
p.s.: Paul, I very much enjoy your MySQL book.