DROP FUNCTION
說明
DROP FUNCTION 陳述式會刪除暫時或使用者定義的函數 (UDF)。如果函數不存在，會擲回例外狀況。
語法
DROP [ TEMPORARY ] FUNCTION [ IF EXISTS ] function_name
參數
-
function_name
指定現有函數的名稱。函數名稱可以選擇使用資料庫名稱限定。
語法：
[ database_name. ] function_name -
TEMPORARY
應使用來刪除
TEMPORARY函數。 -
IF EXISTS
如果指定，函數不存在時不會擲回例外狀況。
範例
-- Create a permanent function `test_avg`
CREATE FUNCTION test_avg AS 'org.apache.hadoop.hive.ql.udf.generic.GenericUDAFAverage';
-- List user functions
SHOW USER FUNCTIONS;
+----------------+
| function|
+----------------+
|default.test_avg|
+----------------+
-- Create Temporary function `test_avg`
CREATE TEMPORARY FUNCTION test_avg AS
'org.apache.hadoop.hive.ql.udf.generic.GenericUDAFAverage';
-- List user functions
SHOW USER FUNCTIONS;
+----------------+
| function|
+----------------+
|default.test_avg|
| test_avg|
+----------------+
-- Drop Permanent function
DROP FUNCTION test_avg;
-- Try to drop Permanent function which is not present
DROP FUNCTION test_avg;
Error: Error running query:
org.apache.spark.sql.catalyst.analysis.NoSuchPermanentFunctionException:
Function 'default.test_avg' not found in database 'default'; (state=,code=0)
-- List the functions after dropping, it should list only temporary function
SHOW USER FUNCTIONS;
+--------+
|function|
+--------+
|test_avg|
+--------+
-- Drop Temporary function
DROP TEMPORARY FUNCTION IF EXISTS test_avg;