如何使用 jdbc 驱动程序在 java 中正确执行“SET”查询

Question

I am able to make a connection to my database but unable to execute a SET query properly. From looking at the documentation, I should be using execute not executeQuery or executeUpdate . I have a working connection and this is the rest:

 try (Statement st = connection.createStatement()) {
        boolean result = st.execute("SET search_path TO '712275-8S8DH-74DASS'");
        ResultSet queryResult = st.executeQuery("SELECT MAX(customer.last_updated) from customer");
        while (queryResult.next()) {
          String lastUpdated = queryResult.getString("last_updated");
        }
 } catch (SQLException ex) {
        LOGGER.info(ex.getMessage());
 }

I get these exceptions: The column name last_updated was not found in this ResultSet. and No data from query which makes me think the search_path hasn't been set properly because when I make a direct connection using psql , I am able to get results by running

postgres=> SET search_path TO '712275-8S8DH-74DASS';
SET
postgres=> SELECT MAX(customer.last_updated) from customer;
[expected result]

Answer 1

Your query doesn't return the result in a column called last_updated . That's because you are doing an aggregate operation. I think the column returned by the query is called max .

This might work:

String lastUpdated = queryResult.getString("max");

Or you can use an alias:

ResultSet queryResult = st.executeQuery("SELECT MAX(customer.last_updated) as last_updated from customer");