使用Java，用数组中的值更新每一行中的一列的最佳方法是什么？ （SQLite）

Question

Today is my first day using SQLite. I am using Java to interact with an SQLite database that contains fields called ID, NAME, CITY. I would like to take every record in the database and replace the CITY field with a value from an array. Here is what I tried, but realized right away it was wrong. I believe the query is replacing every record 3 times which gives the result that each CITY field is 'Compton'. I am not sure on what is a good or efficient way to do this.

public void update(String cities[]) throws SQLException {

    PreparedStatement updateCity = null;
    Connection con = null;
    String updateString = "update SUPPLIERS set CITY = ?";

    try {

        Class.forName("org.sqlite.JDBC");
        con = DriverManager.getConnection("jdbc:sqlite:suppliers.db);
        con.setAutoCommit(false);
        updateCity = con.prepareStatement(updateString);

        for (int i = 0; i < cities.length; i++) {
           updateCity.setString(1, cities[i]);
           updateCity.executeUpdate();
           con.commit();
        }
    } catch (Exception e) {

        e.printStackTrace();

        if (con != null) {

            try {

                System.err.print("Transaction is being rolled back");
                con.rollback();

            } catch (SQLException excep) {

                excep.printStackTrace();
            }
        }

    } finally {
        if (updateCity != null) {

            updateCity.close();
        }

        con.setAutoCommit(true);

        con.close();
    }
}

I was calling the method like so instance.update(new String[]{"san diego", "los angeles", "Compton"}); . I would like to know how to go about doing this with a PreparedStatement if possible, but if this is not the best way to go, please post an alternative suggestion.

Note: This is not my code, it is code taken from SQLite Java Tutorials .

Answer 1

Your update statement will update ever record in the table each time it is called. If you want the statement to update only one record at a time, you will need to change your update statement to something like this:

update SUPPLIERS set CITY = ? where ID = ?

If you want to update all records, you'll need to execute a query to get all of the IDs. A query like this should work:

select ID from SUPPLIERS

Then for each ID returned, call the update statement using that ID and whatever city you wish to update the record with.