“通用"使用JDBC的当前时间函数 [英] "Generic" current time function using JDBC

问题描述

当我们使用JPA和JPQL时，我们可以使用一些日期/时间表达式，使查询DMBS独立.例如，假设我要在数据库中设置会话的结束时间，则可以简单地使用CURRENT_TIMESTAMP表达式，如下所示:

When we work with JPA and JPQL we can use some date/time expressions which make the query DMBS independent. For instance let's say if I want to set the ending time of a session in my database I could simply use CURRENT_TIMESTAMP expression as follows:

String jpql = "UPDATE SessionJpa s SET s.end = CURRENT_TIMESTAMP WHERE s.id = :id";

entityManager.getTransaction().begin();
Query query = entityManager.createQuery(jpql);
            query.setParameter("id", someIdValue);
            query.executeUpdate();
entityManager.getTransaction().commit();

这样，同一JPQL应该可以与DBMS一起用于Oracle，MySQL，PostreSQL等.

This way the same JPQL should work with Oracle, MySQL, PostreSQL, etc as DBMS.

现在我的问题是:使用JDBC而不是JPA时是否可以实现相同的目的?

Now my question: Is there a way to achieve the same when using JDBC instead of JPA?

这是我到目前为止所拥有的:

This is what I have so far:

String sql = "UPDATE Sessions SET end = SYSDATE WHERE id = ?";

try (Connection connection = dataSource.getConnection();
    PreparedStatement statement = connection.prepareStatement(sql)) {

        statement.setLong(1, someIdValue);
        int updatedRows = statement.executeUpdate();

} catch(SQLException ex) {
    Logger.getLogger(SessionsBean.class.getName()).log(Level.SEVERE, null, ex);
}

但是SYSDATE当然不是通用表达式，它最有可能仅与Oracle作为DBMS一起使用.

But of course SYSDATE is not a generic expression and it will work only with Oracle as DBMS most likely.

推荐答案

您可以在此处找到相关的讨论- Oracle的CURRENT_TIMESTAMP函数是否真的是一个功能?.

You can find a related discussion here - Is Oracle's CURRENT_TIMESTAMP function really a function?.

总结是-CURRENT_TIMESTAMP是由SQL标准定义的，任何兼容的数据库系统都应该识别它.

Summary is that - CURRENT_TIMESTAMP is defined by the SQL standard and any compliant database system should recognize it.

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