Revert "Revert "added""

This reverts commit 6f042a7.

Author: soyeric128

docs/en/guides/54-query/08-stored-procedure.md

@@ -6,7 +6,7 @@ A stored procedure is a set of executable commands or logic blocks stored within
 
 ## Supported Languages
 
-**Databend currently supports [SQL scripting](#sql-scripting) only**. Using SQL scripting, users can define procedures with control flow constructs like loops (FOR, WHILE, REPEAT) and conditionals (IF, CASE), enabling complex logic and effective multi-step operations.
+**Databend currently supports [SQL Scripting](#sql-scripting) only**. Using SQL scripting, users can define procedures with control flow constructs like loops (FOR, WHILE, REPEAT) and conditionals (IF, CASE), enabling complex logic and effective multi-step operations.
 
 ### SQL Scripting
 
@@ -84,9 +84,57 @@ In Databend, stored procedures support a rich set of features to allow users to
   - **Single-line comments**: `-- comment`
   - **Multi-line comments**: `/* comment */`
 
+## Limitations
+
+The following limitations apply when working with stored procedures:
+
+- Stored procedures are an experimental feature. Before working with them, set `enable_experimental_procedure` to 1;
+
+    ```sql
+    SET enable_experimental_procedure = 1;
+    ```
+
+- Stored procedures return results as strings, regardless of the specified return type, without enforcing the declared type on the returned value.
+
 ## Managing Stored Procedures
 
 Databend offers a range of commands for managing stored procedures. For more details, see [Stored Procedure](/sql/sql-commands/ddl/procedure/).
 
 ## Usage Example
 
+Suppose we want to calculate the sum of all even numbers within a given range. This stored procedure accepts a starting value start_val and an ending value end_val and calculates the sum of all even numbers within this range.
+
+```sql
+SET enable_experimental_procedure = 1;
+
+CREATE PROCEDURE sum_even_numbers(start_val UInt8, end_val UInt8) 
+RETURNS UInt8 NOT NULL 
+LANGUAGE SQL 
+COMMENT='Calculate the sum of all even numbers' 
+AS $$
+BEGIN
+    LET sum := 0;
+    FOR i IN start_val TO end_val DO
+        IF i % 2 = 0 THEN
+            sum := sum + i;
+        END IF;
+    END FOR;
+    
+    RETURN sum;
+END;
+$$;
+```
+
+If we want to calculate the sum of all even numbers from 1 to 10, we can call the procedure as follows:
+
+```sql
+CALL PROCEDURE sum_even_numbers(1, 10);
+
+-- Result: 2 + 4 + 6 + 8 + 10 = 30
+┌────────┐
+│ Result │
+├────────┤
+│ 30     │
+└────────┘
+```
+

docs/en/sql-reference/10-sql-commands/00-ddl/18-procedure/create-procedure.md

@@ -27,7 +27,7 @@ $$;
 | `<procedure_name>`                      | Name of the procedure.                                                                                                    |
 | `<parameter_name> <data_type>`          | Input parameters (optional), each with a specified data type. Multiple parameters can be defined and separated by commas. |
 | `RETURNS <return_data_type> [NOT NULL]` | Specifies the data type of the return value. `NOT NULL` ensures the returned value cannot be NULL.                        |
-| `LANGUAGE`                              | Specifies the language in which the procedure body is written. Currently, only `SQL` is supported.                        |
+| `LANGUAGE`                              | Specifies the language in which the procedure body is written. Currently, only `SQL` is supported. For details, see [SQL Scripting](/guides/query/stored-procedure#sql-scripting).                       |
 | `COMMENT`                               | Optional text describing the procedure.                                                                                   |
 | `AS ...`                                | Encloses the procedure body, which contains SQL statements, variable declarations, loops, and a  RETURN statement.        |