add if exists to drop function (#2101)

* add if exists to drop function

* add if exists to drop function

Author: ShanlanLi

docs/sql/commands/sql-drop-function.md

@@ -13,35 +13,14 @@ Use the `DROP FUNCTION` command to remove an existing [user-defined function (UD
 ## Syntax
 
 ```sql
-DROP FUNCTION function_name [ ( argument_type [, ...] ) ] ;
+DROP FUNCTION [ IF EXISTS ] function_name [ ( argument_type [, ...] ) ] ;
 ```
 
-import rr from '@theme/RailroadDiagram'
-
-export const svg = rr.Diagram(
-    rr.Sequence(
-        rr.Terminal('DROP FUNCTION'),
-        rr.NonTerminal('function_name'),
-        rr.Optional(
-            rr.Sequence(
-                rr.Terminal('('),
-                rr.OneOrMore(
-                    rr.NonTerminal('argument_type', 'skip'),
-                    ','
-                ),
-                rr.Terminal(')'),
-            ),
-        ),
-        rr.Terminal(';'),
-    )
-);
-
-<drawer SVG={svg} />
-
 | Parameter or clause           | Description                                           |
 |-------------------------------|-------------------------------------------------------|
 | *function_name*               | Name of the UDF you want to drop.           |
 | ( *argument_type* [ , ... ] ) | Optional: Argument types of the function.<br/>Specify the argument types when the name of the function you want to drop isn't unique within the schema. |
+|IF EXISTS| Do not return an error if the specified function does not exist. A notice is issued in this case. |
 
 ## Usage
 

versioned_docs/version-1.7/sql/commands/sql-drop-function.md

@@ -13,35 +13,14 @@ Use the `DROP FUNCTION` command to remove an existing [user-defined function (UD
 ## Syntax
 
 ```sql
-DROP FUNCTION function_name [ ( argument_type [, ...] ) ] ;
+DROP FUNCTION [ IF EXISTS ] function_name [ ( argument_type [, ...] ) ] ;
 ```
 
-import rr from '@theme/RailroadDiagram'
-
-export const svg = rr.Diagram(
-    rr.Sequence(
-        rr.Terminal('DROP FUNCTION'),
-        rr.NonTerminal('function_name'),
-        rr.Optional(
-            rr.Sequence(
-                rr.Terminal('('),
-                rr.OneOrMore(
-                    rr.NonTerminal('argument_type', 'skip'),
-                    ','
-                ),
-                rr.Terminal(')'),
-            ),
-        ),
-        rr.Terminal(';'),
-    )
-);
-
-<drawer SVG={svg} />
-
 | Parameter or clause           | Description                                           |
 |-------------------------------|-------------------------------------------------------|
 | *function_name*               | Name of the UDF you want to drop.           |
 | ( *argument_type* [ , ... ] ) | Optional: Argument types of the function.<br/>Specify the argument types when the name of the function you want to drop isn't unique within the schema. |
+|IF EXISTS| Do not return an error if the specified function does not exist. A notice is issued in this case. |
 
 ## Usage
 

versioned_docs/version-1.8/sql/commands/sql-drop-function.md

@@ -13,35 +13,14 @@ Use the `DROP FUNCTION` command to remove an existing [user-defined function (UD
 ## Syntax
 
 ```sql
-DROP FUNCTION function_name [ ( argument_type [, ...] ) ] ;
+DROP FUNCTION [ IF EXISTS ] function_name [ ( argument_type [, ...] ) ] ;
 ```
 
-import rr from '@theme/RailroadDiagram'
-
-export const svg = rr.Diagram(
-    rr.Sequence(
-        rr.Terminal('DROP FUNCTION'),
-        rr.NonTerminal('function_name'),
-        rr.Optional(
-            rr.Sequence(
-                rr.Terminal('('),
-                rr.OneOrMore(
-                    rr.NonTerminal('argument_type', 'skip'),
-                    ','
-                ),
-                rr.Terminal(')'),
-            ),
-        ),
-        rr.Terminal(';'),
-    )
-);
-
-<drawer SVG={svg} />
-
 | Parameter or clause           | Description                                           |
 |-------------------------------|-------------------------------------------------------|
 | *function_name*               | Name of the UDF you want to drop.           |
 | ( *argument_type* [ , ... ] ) | Optional: Argument types of the function.<br/>Specify the argument types when the name of the function you want to drop isn't unique within the schema. |
+|IF EXISTS| Do not return an error if the specified function does not exist. A notice is issued in this case. |
 
 ## Usage