DROP FUNCTION

Removes a function.

Syntax

DROP FUNCTION [IF EXISTS] <name> ( [ [arg_mode] [arg_name] arg_type [, ...] ] )
    [CASCADE | RESTRICT]

IF EXISTS

If you include IF EXISTS in your command, no error will reported if the specified function does not exist. A notice will be issued instead.
<name>

The name of the function. You can prefix the name with a schema name to remove the function from the specified schema.
<arg_mode>

The mode of the argument, which can be IN, OUT, INOUT, or VARIADIC. If omitted, the default value IN will be used. You do not need to list OUT arguments because DROP FUNCTION uses only input arguments to identify the function.
<arg_name>

The name of the argument.

Argument names are not necessary, since DROP FUNCTION does not use argument names to identify the function.
<arg_type>

The data type of the argument. This parameter is required to identify the function since different functions with the same name can exist.
CASCADE or RESTRICT

Whether to drop the function and its dependent objects if dependent objects exit. Supported options include:
- CASCADE: specifies to drop the dependent objects along with the function.
- RESTRICT: specifies to reject the drop operation and is the default.

Remove the square root function:

DROP FUNCTION sqrt(integer);

Standard SQL does not support DROP FUNCTION.