prepared statement and IN clause

[martin samm]

does anyone know how to handle an IN clause where the number of values in the IN clause may vary when using a PreparedStatement, i.e. i want to code something like :
select * from users where username in (?)
where i want to substitute the ? with any number of values. I realise i could build this up as normal Statement but want to use the efficiency of PreparedStatements. Also i realise i could use and exists and a subselect possibly, but this statement need to be portable accross databases including MySQL
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martin samm
[e-mail]

[Jamie Robertson]

there is no dynamic way to decide how many ? are needed for each individual query. You have to decide at the time of the prepareStatement() the number of ? needed for your query. You can prepare a new statement for each query though, and append the number of ? needed for that query. You would do use it if you wanted all the benefits of PreparedStatement (such as special character handling) but would not have the all performance benefits as if you reuse the PreparedStatement
eg.

String query = "select * from table1 where id in(?";
for (int i = 0; i< numberOfParameters; i++)
{
query = query + ",?";
}
query = query + ")";
PreparedStatement ps = con.prepareStatement(query);
....

but you can't decide after you prepare the preparedStatement

PreparedStatement ps = con.prepareStatement("select * from...where id in(?)");
//can not change the number of parameters now, you are limited to one ?

I haven't taken a look at the jdk1.4 yet (and specifically jdbc 3.0) but up to the jdk1.3.x it is not possible
Jamie