Question

我的表是：

 id  user   date
 ---|-----|------------|
 1  | ab  | 2011-03-04 |
 2  | ab  | 2016-03-04 |
 3  | cd  | 2009-03-04 |
 4  | cd  | 2013-03-03 |
 5  | ef  | 2009-03-03 |

我需要选择每个不同的用户：

“更新”＆gt;日期超过当前日期

结果将是：

 id  user   date
 ---|-----|------------|
 2  | ab  | 2016-03-04 |
 5  | ef  | 2016-03-03 |

“过期”＆gt;日期少于当前日期

结果将是：

 id  user   date
 ---|-----|------------|
 3  | cd  | 2009-03-04 |

我试过了：

SELECT t1.* FROM tmp t1
WHERE t1.date = (SELECT MAX(t2.date)
FROM tmp t2 WHERE t2.user = t1.user
AND YEAR(MAX(t2.date))<(YEAR(CURRENT_TIMESTAMP)-1))
order by user asc

它不起作用。结果集有0行。有任何想法吗？谢谢。它会对我有所帮助..

Answer 1

您的日期采用MM/dd/YYYY的特殊格式，在尝试此处给出的任何答案时，这可能会给您带来麻烦。您应该将04/03/2011转换为2011-04-03。话虽如此，假设您的date列确实是MySQL日期类型，那么以下查询将为您提供所有不同的“更新”用户：

SELECT t1.id, t1.user, t1.date, 'update' AS status
FROM antivirus t1
INNER JOIN
(
    SELECT user, MAX(date) AS date
    FROM antivirus
    GROUP BY user
    HAVING MAX(date) >= CURDATE()
) t2
ON t1.user = t2.user AND t1.date = t2.date

SQLFiddle

请注意，在我的小提琴中，我必须修改样本表中日期输入的格式。

如果您还希望同一查询中的“已过期”用户，则可以添加UNION ALL以及以下内容：

SELECT t1.id, t1.user, t1.date, 'expired' AS status
FROM antivirus t1
INNER JOIN
(
    SELECT user, MAX(date) AS date
    FROM antivirus
    GROUP BY user
    HAVING MAX(date) < CURDATE()
) t2
ON t1.user = t2.user AND t1.date = t2.date

Answer 2

对于大于当前日期的日期：

group by

实际上，我认为你想要一个select user from t group by user having max(`date`) >= curdate();：

def distorted_inputs(data_dir, batch_size):
  """Construct distorted input for CIFAR training using the Reader ops.

  Args:
    data_dir: Path to the CIFAR-10 data directory.
    batch_size: Number of images per batch.

  Returns:
    images: Images. 4D tensor of [batch_size, IMAGE_SIZE, IMAGE_SIZE, 3] size.
    labels: Labels. 1D tensor of [batch_size] size.
  """
  filenames = [os.path.join(data_dir, 'data_batch_%d.bin' % i)
               for i in xrange(1, 6)]
  for f in filenames:
    if not gfile.Exists(f):
      raise ValueError('Failed to find file: ' + f)

  # Create a queue that produces the filenames to read.
  filename_queue = tf.train.string_input_producer(filenames)

  # Read examples from files in the filename queue.
  read_input = read_cifar10(filename_queue)
  reshaped_image = tf.cast(read_input.uint8image, tf.float32)
  distorted_image = reshaped_image

  height = IMAGE_SIZE
  width = IMAGE_SIZE

  # Image processing for training the network. Note the many random
  # distortions applied to the image.

  # Randomly crop a [height, width] section of the image.
  # distorted_image = tf.image.random_crop(reshaped_image, [height, width])

  # Randomly flip the image horizontally.
  # distorted_image = tf.image.random_flip_left_right(distorted_image)

  # Because these operations are not commutative, consider randomizing
  # randomize the order their operation.
  distorted_image = tf.image.random_brightness(distorted_image,
                                               max_delta=63)
  distorted_image = tf.image.random_contrast(distorted_image,
                                             lower=0.2, upper=1.8)

  # Subtract off the mean and divide by the variance of the pixels.
  float_image = tf.image.per_image_whitening(distorted_image)

  # Ensure that the random shuffling has good mixing properties.
  min_fraction_of_examples_in_queue = 0.4
  min_queue_examples = int(NUM_EXAMPLES_PER_EPOCH_FOR_TRAIN *
                           min_fraction_of_examples_in_queue)
  print ('Filling queue with %d CIFAR images before starting to train. '
         'This will take a few minutes.' % min_queue_examples)

  # Generate a batch of images and labels by building up a queue of examples.
  return _generate_image_and_label_batch(float_image, read_input.label,
                                         min_queue_examples, batch_size)

这也适用于较早的日期。

Answer 3

有几点意见：

＆＃34;它没有工作＆＃34;并不是对您观察到的行为的描述。它没有描述查询是否正在执行并返回意外结果，或者查询是否返回错误。

date值显示的值采用奇怪的非MySQL格式。 DATE值的标准格式为YYYY-MM-DD。这让我们想知道名为date的列的实际数据类型是什么。如果它是一个字符串，包含一年中的月份和日期，则会在比较中出现问题。字符串比较是从左到右逐个字符完成的。

在此上下文中使用YEAR()函数非常奇怪。你说你想比较＆＃34; date＆＃34;值。 YEAR函数从日期中提取年份值。所以看起来您的查询只会比较一年。

同样，如果YEAR()函数的参数不是DATE数据类型，则会将该参数隐式转换为DATE。 ..并且为了使隐式转换正常工作，字符串将需要采用＆＃39; YYYY-MM-DD＆＃39;等格式。

此外，子查询看起来在MAX()子句中使用聚合函数WHERE。那是无效的。访问行时，将评估WHERE子句中的谓词。在访问行之后，聚合函数的值将不可用，并且执行group by操作。如果您需要聚合条件，则可以进入HAVING子句。

Answer 4

感谢@TimBiegeleisen的回答.. 我已经尝试过这段代码而且它有效..

此代码用于显示“更新”行：

select a.* from tmp a 
inner join
(select user, max(date) as date from tmp group by user)
b on a.user=b.user and a.date=b.date
where year(a.date +interval 1 year) >= year(current_date())
order by a.user

这用于显示'过期'行：

select a.* from tmp a
inner join
(select user, max(date) as date from tmp group by user)
b on a.user=b.user and a.date=b.date
where year(a.date +interval 1 year) < year(current_date())
order by a.user

我希望我的问题和所有答案能够帮助解决其他问题。

选择具有最近每个用户日期的行，其中日期大于当前日期

4 个答案: