DESCRIBE FUNCTIONDESCRIBE FUNCTION

Gibt die grundlegenden Metadateninformationen einer vorhandenen Funktion zurück.Returns the basic metadata information of an existing function. Die Metadateninformationen umfassen den Funktionsnamen, die implementierende Klasse und die Verwendungs Details.The metadata information includes the function name, implementing class and the usage details. Wenn die optionale- EXTENDED Option angegeben wird, werden die grundlegenden Metadateninformationen zusammen mit den erweiterten Verwendungs Informationen zurückgegeben.If the optional EXTENDED option is specified, the basic metadata information is returned along with the extended usage information.

SyntaxSyntax

{ DESC | DESCRIBE } FUNCTION [ EXTENDED ] function_name

ParameterParameters

  • function_namefunction_name

    Der Name einer vorhandenen Funktion im System.The name of an existing function in the system. Der Name der Funktion kann optional mit einem Datenbanknamen qualifiziert werden.The function name may be optionally qualified with a database name. Wenn function_name mit einer Datenbank qualifiziert ist, wird die Funktion von der benutzerdefinierten Datenbank aufgelöst; andernfalls wird Sie aus der aktuellen Datenbank aufgelöst.If function_name is qualified with a database then the function is resolved from the user specified database, otherwise it is resolved from the current database.

    Syntax:[database_name.] function_nameSyntax: [database_name.] function_name

BeispieleExamples

-- Describe a builtin scalar function.
-- Returns function name, implementing class and usage
DESC FUNCTION abs;
+-------------------------------------------------------------------+
|function_desc                                                      |
+-------------------------------------------------------------------+
|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.
DESC FUNCTION EXTENDED abs;
+-------------------------------------------------------------------+
|function_desc                                                      |
+-------------------------------------------------------------------+
|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
DESC FUNCTION max;
+--------------------------------------------------------------+
|function_desc                                                 |
+--------------------------------------------------------------+
|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.
DESC FUNCTION EXTENDED explode
+---------------------------------------------------------------+
|function_desc                                                  |
+---------------------------------------------------------------+
|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, uses   |
| 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                                                      |
+---------------------------------------------------------------+