Does “select for update” prevent other connections inserting when the row is not present

Question

I\'m interested in whether a select for update query will lock a non-existent row.

e.g.

Table FooBar with two columns, foo and bar, foo has a un

Answer 1

In Oracle, the SELECT ... FOR UPDATE has no effect on a non-existent row (the statement simply raises a No Data Found exception). The INSERT statement will prevent a duplicates of unique/primary key values. Any other transactions attempting to insert the same key values will block until the first transaction commits (at which time the blocked transaction will get a duplicate key error) or rolls back (at which time the blocked transaction continues).