DESCRIBE FUNCTION
适用于: Databricks SQL Databricks Runtime
返回现有函数的基本元数据信息。 元数据信息包括函数名称、实现类和使用详细信息。 如果指定了可选的 EXTENDED
选项,则将返回基本元数据信息和详细使用信息。
语法
{ DESC | DESCRIBE } FUNCTION [ EXTENDED ] function_name
参数
function_name
元存储中现有函数的名称。 可选择使用架构名称来限定函数名称。 如果
function_name
使用架构进行限定,则从用户指定的架构解析该函数,否则从当前架构解析该函数。
示例
-- 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)