自动提交设置为false时，select是否返回最后插入的行？

Question

Say I have a table named and a column named with the format user1, user2 ..

I want to insert users into this table in a loop and value of every entry depends on the one's before. Value of the new entry is generated by the alphabetically greatest entry in the table, namely .

Since it's possible in JDBC API to getGeneratedKeys after an insert while AutoCommit set to false;

In a situation like given below:

connection.setAutoCommit(false);
while(someCondition)
{
    ResultSet rs = connection.createStatement("select max(username) from users").executeQuery();
    if(rs.next())
    { 
        name= rs.getString("username"); //returns user1
    }
    String newName = generateNewName(name); // simply makes user1 -> user2

    connection.createStatement("insert into users (name,...) values ("+newName+",...)").executeUpdate(); ///and inserts..
}

does the query return the last inserted value or it returns the max column in the table before I start the loop ?

Answer 1

First, to make sure you see all changes on the database immediately prefer TransactionIsolation of READ_UNCOMMITED over using auto commit. Alternatively using auto commit everywhere would do the job, too.

Once you made sure you see every db change immediately, the database will send you the maximum user from some time during the selects execution. But once you actually receive the result there might be additional users created by others threads. Thus this will only work for a single thread working and most likely that doesn't make any sense nowadays.

TL:DR No, don't do it!