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- Log Storage
- Log Search and Analytic
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- Configuring Indexes
- Analysis Syntax
- Analytic Functions
- String Function
- Date and Time Functions
- IP Geographic Function
- URL Function
- Mathematical Calculation Functions
- Mathematical Statistical Function
- General Aggregate Functions
- Geospatial Function
- Binary String Function
- Estimation Function
- Type Conversion Function
- Logical Function
- Operators
- Bitwise Operation
- Regular Expression Function
- Lambda Function
- Conditional Expressions
- Array Functions
- Interval-Valued Comparison and Periodicity-Valued Comparison Functions
- JSON Functions
- Window Functions
- Quick Analysis
- Context Search and Analysis
- Downloading Log
- Data Processing
- Creating a Processing Task
- Viewing Data Processing Details
- Data Processing Functions
- Function Overview
- Key-Value Extraction Functions
- Enrichment Functions
- Flow Control
- Row Processing Functions
- Field Processing Functions
- Value Structuring Functions
- Regular Expression Processing Functions
- Time Value Processing Functions
- String Processing Functions
- Type Conversion Functions
- Logical Expression Functions
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- Log Shipping
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- Glossary
This document introduces the basic syntax and examples of estimation functions.
| Function | Syntax | Description |
|---|---|---|
| approx_distinct | approx_distinct(x) | Returns the approximate number of distinct input values (column x). |
| approx_percentile | approx_percentile(x,percentage) | Sorts the values in the x column in ascending order and returns the value approximately at the given `percentage` position. |
| approx_percentile(x,array[percentage01, percentage02...]) | Sorts the values in the x column in ascending order and returns the values approximately at the given `percentage` positions (percentage01, percentage02...). |
approx_distinct
The approx_distinct function is used to get the approximate number of distinct input values of a field.
Syntax
approx_distinct(x)
Parameter description
| Parameter | Description |
|---|---|
| x | The parameter value can be of any type. |
Return value type
bigint
Example
Use the count function to calculate the PV value and use the approx_distinct function to get the approximate number of distinct input values of the client_ip field and use it as the UV value.
* | SELECT count(*) AS PV, approx_distinct(ip) AS UV
approx_percentile
The approx_percentile function is used to sort the values of a target field in ascending order and return the values approximately at the given percentage position.
Syntax
- Return the value (double) approximately at the given
percentagepositionapprox_percentile(x, percentage) - Return the value (array) approximately at the given
percentagepositions (percentage01,percentage02...)approx_percentile(x, array[percentage01,percentage02...])
Parameter description
| Parameter | Description |
|---|---|
| x | Value type: double |
| percentage | Value range: [0,1] |
Return value type
double or array
Example
Example 1: sort the values of the resTotalTime column and return the value of resTotalTime approximately at the 50% position
* | select approx_percentile(resTotalTime,0.5)
Example 2: sort the values of the resTotalTime column and return the values of resTotalTime approximately at the 10%, 20%, and 60% positions
* | select approx_percentile(resTotalTime, array[0.2,0.4,0.6])
Yes
No
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