From 9a61f207e94aaa11ea481067fd1201c669d6a44d Mon Sep 17 00:00:00 2001 From: Ganlin Zhao <36554565+glzhao89@users.noreply.github.com> Date: Thu, 17 Mar 2022 13:36:22 +0800 Subject: [PATCH] Update docs.md --- documentation20/en/12.taos-sql/docs.md | 62 ++++++++++++++++++++++++++ 1 file changed, 62 insertions(+) diff --git a/documentation20/en/12.taos-sql/docs.md b/documentation20/en/12.taos-sql/docs.md index cbfe9e7041..fc7dbe7af2 100755 --- a/documentation20/en/12.taos-sql/docs.md +++ b/documentation20/en/12.taos-sql/docs.md @@ -1404,6 +1404,68 @@ TDengine supports aggregations over data, they are listed below: 2022-01-01 08:00:07.000000000 | 9 | 2 | Query OK, 6 row(s) in set (0.002613s) ``` +- **HISTOGRAM** + ```mysql + SELECT HISTOGRAM(field_name，bin_type, bin_description, normalized) FROM tb_name [WHERE clause]; + ``` + Function：Returns count of data points in user-specified ranges. + + Return Data Type：Double or INT64, depends on normalized parameter settings. + + Applicable Fields：Numerical types. + + Applied to: **table stable**. + + Note： + 1. This function is supported since 2.6.0.0. + 2. bin_type: parameter to indicate the bucket type, valid inputs are: "user_input", "linear_bin", "log_bin"。 + 3）bin_description: parameter to describe how to generate buckets，can be in the following JSON formats for each bin_type respectively: + - "user_input": "[1, 3, 5, 7]" + User defined specified bin values. + + - "linear_bin": "{"start": 0.0, "width": 5.0, "count": 5, "infinity": true}" + "start" - bin starting point. + "width" - bin offset. + "count" - number of bins generated. + "infinity" - whether to add（-inf, inf）as start/end point in generated set of bins. + The above "linear_bin" descriptor generates a set of bins: [-inf, 0.0, 5.0, 10.0, 15.0, 20.0, +inf]. + + - "log_bin": "{"start":1.0, "factor": 2.0, "count": 5, "infinity": true}" + "start" - bin starting point. + "factor" - exponential factor of bin offset. + "count" - number of bins generated. + "infinity" - whether to add（-inf, inf）as start/end point in generated range of bins. + The above "log_bin" descriptor generates a set of bins:[-inf, 1.0, 2.0, 4.0, 8.0, 16.0, +inf]. + 4）normalized: setting to 1/0 to turn on/off result normalization. + + Example： + ```mysql + taos> SELECT HISTOGRAM(voltage, "user_input", "[1,3,5,7]", 1) FROM meters; + histogram(voltage, "user_input", "[1,3,5,7]", 1) | + ======================================================= + {"lower_bin":1, "upper_bin":3, "count":0.333333} | + {"lower_bin":3, "upper_bin":5, "count":0.333333} | + {"lower_bin":5, "upper_bin":7, "count":0.333333} | + Query OK, 3 row(s) in set (0.004273s) + + taos> SELECT HISTOGRAM(voltage, 'linear_bin', '{"start": 1, "width": 3, "count": 3, "infinity": false}', 0) FROM meters; + histogram(voltage, 'linear_bin', '{"start": 1, "width": 3, " | + =================================================================== + {"lower_bin":1, "upper_bin":4, "count":3} | + {"lower_bin":4, "upper_bin":7, "count":3} | + {"lower_bin":7, "upper_bin":10, "count":3} | + Query OK, 3 row(s) in set (0.004887s) + + taos> SELECT HISTOGRAM(voltage, 'log_bin', '{"start": 1, "factor": 3, "count": 3, "infinity": true}', 0) FROM meters; + histogram(voltage, 'log_bin', '{"start": 1, "factor": 3, "count" | + =================================================================== + {"lower_bin":-inf, "upper_bin":1, "count":3} | + {"lower_bin":1, "upper_bin":3, "count":2} | + {"lower_bin":3, "upper_bin":9, "count":6} | + {"lower_bin":9, "upper_bin":27, "count":3} | + {"lower_bin":27, "upper_bin":inf, "count":1} | + ``` + ## Time-dimension Aggregation -- GitLab