running_difference

description

Syntax

T running_difference(T x)

Calculates the difference between successive row values ​​in the data block. The result of the function depends on the affected data blocks and the order of data in the block.

The rows order used during the calculation of running_difference can differ from the order of rows returned to the user. The function will be deprecated in the future. Please use window function instead, below is the example:

  1. -- running difference(x)
  2. SELECT running_difference(x) FROM t ORDER BY k;
  4. -- window function
  5. SELECT x - lag(x, 1, 0) OVER (ORDER BY k) FROM t;

Arguments

x - A list of data.TINYINT,SMALLINT,INT,BIGINT,LARGEINT,FLOAT,DOUBLE,DATE,DATETIME,DECIMAL

Returned value

Returns 0 for the first row and the difference from the previous row for each subsequent row

example

  1. DROP TABLE IF EXISTS running_difference_test;
  3. CREATE TABLE running_difference_test (
  4.     `id` int NOT NULL COMMENT 'id',
  5.     `day` date COMMENT 'day', 
  6.     `time_val` datetime COMMENT 'time_val',
  7.     `doublenum` double NULL COMMENT 'doublenum'
  8. )
  9. DUPLICATE KEY(id) 
  10. DISTRIBUTED BY HASH(id) BUCKETS 3 
  11. PROPERTIES ( 
  12.     "replication_num" = "1"
  13. ); 
  15. INSERT into running_difference_test (id, day, time_val,doublenum) values ('1', '2022-10-28', '2022-03-12 10:41:00', null),
  16.                                                    ('2','2022-10-27', '2022-03-12 10:41:02', 2.6),
  17.                                                    ('3','2022-10-28', '2022-03-12 10:41:03', 2.5),
  18.                                                    ('4','2022-9-29', '2022-03-12 10:41:03', null),
  19.                                                    ('5','2022-10-31', '2022-03-12 10:42:01', 3.3),
  20.                                                    ('6', '2022-11-08', '2022-03-12 11:05:04', 4.7); 
  22. SELECT * from running_difference_test ORDER BY id ASC;
  24. +------+------------+---------------------+-----------+
  25. | id   | day        | time_val            | doublenum |
  26. +------+------------+---------------------+-----------+
  27. |    1 | 2022-10-28 | 2022-03-12 10:41:00 |      NULL |
  28. |    2 | 2022-10-27 | 2022-03-12 10:41:02 |       2.6 |
  29. |    3 | 2022-10-28 | 2022-03-12 10:41:03 |       2.5 |
  30. |    4 | 2022-09-29 | 2022-03-12 10:41:03 |      NULL |
  31. |    5 | 2022-10-31 | 2022-03-12 10:42:01 |       3.3 |
  32. |    6 | 2022-11-08 | 2022-03-12 11:05:04 |       4.7 |
  33. +------+------------+---------------------+-----------+
  35. SELECT
  36.     id,
  37.     running_difference(id) AS delta
  38. FROM
  39. (
  40.     SELECT
  41.         id,
  42.         day,
  43.         time_val,
  44.         doublenum
  45.     FROM running_difference_test
  46. )as runningDifference ORDER BY id ASC;
  48. +------+-------+
  49. | id   | delta |
  50. +------+-------+
  51. |    1 |     0 |
  52. |    2 |     1 |
  53. |    3 |     1 |
  54. |    4 |     1 |
  55. |    5 |     1 |
  56. |    6 |     1 |
  57. +------+-------+
  59. SELECT
  60.     day,
  61.     running_difference(day) AS delta
  62. FROM
  63. (
  64.     SELECT
  65.         id,
  66.         day,
  67.         time_val,
  68.         doublenum
  69.     FROM running_difference_test
  70. )as runningDifference ORDER BY id ASC;
  72. +------------+-------+
  73. | day        | delta |
  74. +------------+-------+
  75. | 2022-10-28 |     0 |
  76. | 2022-10-27 |    -1 |
  77. | 2022-10-28 |     1 |
  78. | 2022-09-29 |   -29 |
  79. | 2022-10-31 |    32 |
  80. | 2022-11-08 |     8 |
  81. +------------+-------+
  83. SELECT
  84.     time_val,
  85.     running_difference(time_val) AS delta
  86. FROM
  87. (
  88.     SELECT
  89.         id,
  90.         day,
  91.         time_val,
  92.         doublenum
  93.     FROM running_difference_test
  94. )as runningDifference ORDER BY id ASC;
  96. +---------------------+-------+
  97. | time_val            | delta |
  98. +---------------------+-------+
  99. | 2022-03-12 10:41:00 |     0 |
  100. | 2022-03-12 10:41:02 |     2 |
  101. | 2022-03-12 10:41:03 |     1 |
  102. | 2022-03-12 10:41:03 |     0 |
  103. | 2022-03-12 10:42:01 |    58 |
  104. | 2022-03-12 11:05:04 |  1383 |
  105. +---------------------+-------+
  107. SELECT
  108.     doublenum,
  109.     running_difference(doublenum) AS delta
  110. FROM
  111. (
  112.     SELECT
  113.         id,
  114.         day,
  115.         time_val,
  116.         doublenum
  117.     FROM running_difference_test
  118. )as runningDifference ORDER BY id ASC;
  120. +-----------+----------------------+
  121. | doublenum | delta                |
  122. +-----------+----------------------+
  123. |      NULL |                 NULL |
  124. |       2.6 |                 NULL |
  125. |       2.5 | -0.10000000000000009 |
  126. |      NULL |                 NULL |
  127. |       3.3 |                 NULL |
  128. |       4.7 |   1.4000000000000004 |
  129. +-----------+----------------------+

keywords

running_difference