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DESCRIBE 函式

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適用於： 檢查標示為是 Databricks SQL 檢查標示為是 Databricks Runtime

傳回現有函式的基本元數據資訊。 元數據資訊包括函式名稱、實作類別和使用方式詳細數據。 如果指定了選擇性 EXTENDED 選項，則會傳回基本元數據資訊以及擴充的使用方式資訊。

語法

{ DESC | DESCRIBE } FUNCTION [ EXTENDED ] function_name

參數

  • function_name

    中繼存放區中現有函式的名稱。 函式名稱可能選擇性地以架構名稱限定。 如果 function_name 以架構限定，則函式會從使用者指定的架構解析，否則會從目前的架構解析。

範例

-- Describe a builtin scalar function.
-- Returns function name, implementing class and usage
> DESCRIBE FUNCTION abs;
 Function: abs
 Class: org.apache.spark.sql.catalyst.expressions.Abs
 Usage: abs(expr) - Returns the absolute value of the numeric value.

-- Describe a builtin scalar function.
-- Returns function name, implementing class and usage and examples.
> DESCRIBE FUNCTION EXTENDED abs;
 Function: abs
 Class: org.apache.spark.sql.catalyst.expressions.Abs
 Usage: abs(expr) - Returns the absolute value of the numeric value.
 Extended Usage:
     Examples:
       > SELECT abs(-1);
        1

-- Describe a builtin aggregate function
> DESCRIBE FUNCTION max;
 Function: max
 Class: org.apache.spark.sql.catalyst.expressions.aggregate.Max
 Usage: max(expr) - Returns the maximum value of `expr`.

-- Describe a builtin user defined aggregate function
-- Returns function name, implementing class and usage and examples.
> DESCRIBE FUNCTION EXTENDED explode;
 Function: explode
 Class: org.apache.spark.sql.catalyst.expressions.Explode
 Usage: explode(expr) - Separates the elements of array `expr`
  into multiple rows, or the elements of map `expr` into
  multiple rows and columns. Unless specified otherwise, use
  the default column name `col` for elements of the array or
  `key` and `value` for the elements of the map.
 Extended Usage:
     Examples:
       > SELECT explode(array(10, 20));
        10
        20

-- Describe a user defined scalar function
> CREATE FUNCTION dice(n INT) RETURNS INT
    NOT DETERMINISTIC
    COMMENT 'An n-sided dice'
    RETURN floor((rand() * n) + 1);

> DESCRIBE FUNCTION EXTENDED dice;
 Function:      default.dice
 Type:          SCALAR
 Input:         n INT
 Returns:       INT
 Comment:       An n-sided dice
 Deterministic: false
 Owner:         user
 Create Time:   Fri Apr 16 10:00:00 PDT 2021
 Body:          floor((rand() * n) + 1)