LINEAR_HISTOGRAM

Description

Syntax

LINEAR_HISTOGRAM(expr, DOUBLE interval[, DOUBLE offset)

linear_histogram 函数用于描述数据分布情况，它使用“等宽”的分桶策略，并按照数据的值大小进行分桶。

参数说明：

• interval：必须项。桶的宽度。
• offset：可选项。默认为 0，范围是 [0, interval)。

Example

mysql> select linear_histogram(a, 2) from histogram_test;
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| linear_histogram(a, cast(2 as DOUBLE))                                                                                                                                                                                                                                                                                                           |
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| {"num_buckets":6,"buckets":[{"lower":0.0,"upper":2.0,"count":2,"acc_count":2},{"lower":2.0,"upper":4.0,"count":4,"acc_count":6},{"lower":4.0,"upper":6.0,"count":4,"acc_count":10},{"lower":6.0,"upper":8.0,"count":4,"acc_count":14},{"lower":8.0,"upper":10.0,"count":4,"acc_count":18},{"lower":10.0,"upper":12.0,"count":2,"acc_count":20}]} |
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

mysql> select linear_histogram(a, 2, 1) from histogram_test;
+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| linear_histogram(a, cast(2 as DOUBLE), cast(1 as DOUBLE))                                                                                                                                                                                                                                   |
+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| {"num_buckets":5,"buckets":[{"lower":1.0,"upper":3.0,"count":4,"acc_count":4},{"lower":3.0,"upper":5.0,"count":4,"acc_count":8},{"lower":5.0,"upper":7.0,"count":4,"acc_count":12},{"lower":7.0,"upper":9.0,"count":4,"acc_count":16},{"lower":9.0,"upper":11.0,"count":4,"acc_count":20}]} |
+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

字段说明：

• num_buckets：桶的数量。
• buckets：直方图所包含的桶。
  • lower：桶的下界。（包含在内）
  • upper：桶的上界。（不包含在内）
  • count：桶内包含的元素数量。
  • acc_count：前面桶与当前桶元素的累计总量。

Keywords

LINEAR_HISTOGRAM