Question

我需要比较Java中的两个日期，但是从数据库获得的日期与插入的日期不同。

@Test
public void testCompareHoraHardcore() {
    String sql = "update solicitacao_viagem set "
            + "hora_retorno=?, id_veiculo=?, id_responsavel_solicitacao=?, "
            + "id_responsavel_autorizante=? where id_solicitacao_viagem=? ";
    Timestamp timestamp1 = new Timestamp(System.currentTimeMillis());
    try {
        PreparedStatement stmt = connection.prepareStatement(sql);
        stmt.setTimestamp(1, timestamp1);
        stmt.setInt(2, 90);
        stmt.setInt(3, 337);
        stmt.setInt(4, 337);
        stmt.setInt(5, 91);
        stmt.executeUpdate();
        stmt.close();
    } catch (SQLException e) {
        e.printStackTrace();
    }
    Timestamp timestamp2 = null;
    try {
        sql = "select * from solicitacao_viagem where id_solicitacao_viagem=?";
        PreparedStatement stmt = connection.prepareStatement(sql);
        stmt.setInt(1, 91);
        stmt.executeQuery();
        ResultSet rs = stmt.executeQuery();
        rs.next();
        timestamp2 = rs.getTimestamp("hora_retorno");
        stmt.close();
    } catch (SQLException e) {
        e.printStackTrace();
    }

    assertEquals(timestamp1.getTime(), timestamp2.getTime());
}

此测试返回：

Testcase: testCompareHoraHardcore(com.model.dao.SolicitacaoViagemDAOTest):  FAILED
expected:<1360553289573> but was:<1360553289000>
junit.framework.AssertionFailedError: expected:<1360553289573> but was:<1360553289000>
at com.model.dao.SolicitacaoViagemDAOTest.testCompareHoraHardcore(SolicitacaoViagemDAOTest.java:349)

为什么MySQL会削减最后三个数字？

我正在使用MySQL 5.5.22和Java（TM）SE运行时环境（版本1.7.0_11-b21）。

列“hora_retorno”是TIMESTAMP。

提前致谢。

Answer 1

MySql将DATETIME和TIMESTAMP存储为秒精度。以下是the documentation

的引用

A DATETIME or TIMESTAMP value can include a trailing fractional seconds
part in up to microseconds(6 digits) precision. 

Although this fractional part is recognized, 
it is discarded from values stored into DATETIME or TIMESTAMP columns

Answer 2

根据这一点，MySQL不会在Timestamp列（或其他日期时间类型）中存储小数秒。 http://dev.mysql.com/doc/refman/5.0/en/fractional-seconds.html

比较Java中的两个日期，一个来自MySQL

2 个答案: