删除sql不删除

Question

我正试图从我的表中删除一个事件。 但是我似乎无法让它发挥作用。 我的SQL语句是：

  public void deleteEvent(String eventName){
    String query = "DELETE FROM `Event` WHERE `eventName` ='"+eventName+"' LIMIT 1";
    db.update(query);
    System.out.println (query);
}

使用MySQL db

Answer 1

尝试使用以下内容：

String query = "DELETE FROM `Event` WHERE `eventName` ='"+eventName+"' LIMIT 1";

        try {
            Connection con = getConnection();
            Statement s = con.createStatement();

            s.execute(query);
        } catch (Exception ex) {
            ex.printStackTrace();
        }

您必须编写getConnection()方法的代码以返回有效的数据库连接。

Answer 2

我建议使用Statement.executeUpdate方法，因为它返回一个整数。 因此，在执行此删除查询后，如果您确实删除了任何记录，您也将获得信息（在这种情况下，您希望此方法返回1，因为您使用的是LIMIT = 1）。 我建议你一旦不需要就关闭Statement，这里是骨架实现：

private void performDelete(Connection conn, String deleteQuery, int expectedResult) throws SQLException {
    Statement stmt = conn.createStatement();
    int result = -1;
    try {
        result = stmt.executeUpdate(deleteQuery);
        if(result != expectedResult) {
            //Here you can check the result. Perhaps you don't need this part
            throw new IllegalStateException("Develete query did not return expected value");
        }
    } catch(SQLException e) {
        //Good practice if you use loggers - log it here and rethrow upper.
        //Or perhaps you don't need to bother in upper layer if the operation
        //was successful or not - in such case, just log it and thats it.
        throw e;
    } finally {
        //This should be always used in conjunction with ReultSets.
        //It is not 100% necessary here, but it will not hurt
        stmt.close();
    }
}