DROP FUNCTION

删除用户定义函数。适用于所有函数类型：Scalar SQL、Tabular SQL 和 Embedded functions。

语法

DROP FUNCTION [ IF EXISTS ] <function_name>

示例

删除 Scalar SQL 函数

-- Create a scalar function
CREATE FUNCTION calculate_bmi(weight FLOAT, height FLOAT)
RETURNS FLOAT
AS $$ weight / (height * height) $$;

-- Drop the function
DROP FUNCTION calculate_bmi;

删除 Tabular SQL 函数

-- Create a table function
CREATE FUNCTION get_employees_by_dept(dept_name VARCHAR)
RETURNS TABLE (id INT, name VARCHAR, department VARCHAR)
AS $$ SELECT id, name, department FROM employees WHERE department = dept_name $$;

-- Drop the function
DROP FUNCTION get_employees_by_dept;

删除 Embedded 函数

-- Create a Python function
CREATE FUNCTION custom_hash(input_str VARCHAR)
RETURNS VARCHAR
LANGUAGE python
HANDLER = 'hash_func'
AS $$
import hashlib
def hash_func(s):
    return hashlib.md5(s.encode()).hexdigest()
$$;

-- Drop the function
DROP FUNCTION custom_hash;

使用 IF EXISTS

-- Safe drop - won't error if function doesn't exist
DROP FUNCTION IF EXISTS non_existent_function;

-- This will succeed without error even if the function doesn't exist