I'm interested in whether a SELECT FOR UPDATE query will lock a non-existent row. Example Table FooBar with two columns, foo and bar , foo has a unique index . Issue query SELECT bar FROM FooBar WHERE foo = ? FOR UPDATE If the first query returns zero rows, issue a query INSERT INTO FooBar (foo, bar) values (?, ?) Now is it possible that the INSERT would cause an index violation or does the SELECT FOR UPDATE prevent that? Interested in behavior on SQLServer (2005/8), Oracle and MySQL.

Does "SELECT FOR UPDATE" prevent other connections inserting when the row is not present?

I'm interested in whether a SELECT FOR UPDATE query will lock a non-existent row.

Table FooBar with two columns, foo and bar, foo has a unique index.

Issue query SELECT bar FROM FooBar WHERE foo = ? FOR UPDATE
If the first query returns zero rows, issue a query
INSERT INTO FooBar (foo, bar) values (?, ?)

Now is it possible that the INSERT would cause an index violation or does the SELECT FOR UPDATE prevent that?

Interested in behavior on SQLServer (2005/8), Oracle and MySQL.