docs: add decode function descr (#2296)

* docs: add decode function descr

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

Co-authored-by: Copilot <[email protected]>

* Update docs/en/guides/51-access-data-lake/02-iceberg.md

Co-authored-by: Copilot <[email protected]>

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

Co-authored-by: Copilot <[email protected]>

* docs: add decode function descr

---------

Co-authored-by: Copilot <[email protected]>

Author: sundy-li

docs/en/guides/51-access-data-lake/02-iceberg.md

@@ -281,6 +281,83 @@ CONNECTION=(
 | `s3.disable-ec2-metadata`         | Option to disable loading credentials from EC2 metadata (typically used with `s3.allow-anonymous`).                                    |
 | `s3.disable-config-load`          | Option to disable loading configuration from config files and environment variables.                                                   |
 
+### Catalog Types
+
+Databend supports four types of Iceberg catalogs:
+
+- REST Catalog
+
+REST catalog uses a RESTful API approach to interact with Iceberg tables.
+
+```sql
+CREATE CATALOG iceberg_rest TYPE = ICEBERG CONNECTION = (
+    TYPE = 'rest'
+    ADDRESS = 'http://localhost:8181'
+    warehouse = 's3://warehouse/demo/'
+    "s3.endpoint" = 'http://localhost:9000'
+    "s3.access-key-id" = 'admin'
+    "s3.secret-access-key" = 'password'
+    "s3.region" = 'us-east-1'
+)
+
+- AWS Glue Catalog
+For Glue catalogs, the configuration includes both Glue service parameters and storage (S3) parameters. The Glue service parameters appear first, followed by the S3 storage parameters (prefixed with "s3.").
+
+```sql
+CREATE CATALOG iceberg_glue TYPE = ICEBERG CONNECTION = (
+    TYPE = 'glue'
+    ADDRESS = 'http://localhost:5000'
+    warehouse = 's3a://warehouse/glue/'
+    "aws_access_key_id" = 'my_access_id'
+    "aws_secret_access_key" = 'my_secret_key'
+    "region_name" = 'us-east-1'
+    "s3.endpoint" = 'http://localhost:9000'
+    "s3.access-key-id" = 'admin'
+    "s3.secret-access-key" = 'password'
+    "s3.region" = 'us-east-1'
+)
+```
+
+- Storage Catalog (S3Tables Catalog)
+
+The Storage catalog requires a table_bucket_arn parameter. Unlike other buckets, S3Tables bucket is not a physical bucket, but a virtual bucket that is managed by S3Tables. You cannot directly access the bucket with a path like `s3://{bucket_name}/{file_path}`. All operations are performed with respect to the bucket ARN.
+
+Properties Parameters
+The following properties are available for the catalog:
+
+```
+profile_name: The name of the AWS profile to use.
+region_name: The AWS region to use.
+aws_access_key_id: The AWS access key ID to use.
+aws_secret_access_key: The AWS secret access key to use.
+aws_session_token: The AWS session token to use.
+```
+
+```sql
+CREATE CATALOG iceberg_storage TYPE = ICEBERG CONNECTION = (
+    TYPE = 'storage'
+    ADDRESS = 'http://localhost:9111'
+    "table_bucket_arn" = 'my-bucket'
+    -- Additional properties as needed
+)
+```
+
+- Hive Catalog (HMS Catalog)
+
+The Hive catalog requires an ADDRESS parameter, which is the address of the Hive metastore. It also requires a warehouse parameter, which is the location of the Iceberg warehouse, usually an S3 bucket or compatible object storage system.
+
+```sql
+CREATE CATALOG iceberg_hms TYPE = ICEBERG CONNECTION = (
+    TYPE = 'hive'
+    ADDRESS = '192.168.10.111:9083'
+    warehouse = 's3a://warehouse/hive/'
+    "s3.endpoint" = 'http://localhost:9000'
+    "s3.access-key-id" = 'admin'
+    "s3.secret-access-key" = 'password'
+    "s3.region" = 'us-east-1'
+)
+```
+
 ### SHOW CREATE CATALOG
 
 Returns the detailed configuration of a specified catalog, including its type and storage parameters.

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

@@ -10,10 +10,10 @@ Defines a stored procedure that executes SQL operations and returns a result.
 ## Syntax
 
 ```sql
-CREATE PROCEDURE <procedure_name>(<parameter_name> <data_type>, ...) 
+CREATE PROCEDURE <procedure_name>(<parameter_name> <data_type>, ...)
 RETURNS <return_data_type> [NOT NULL]
-LANGUAGE <language> 
-[ COMMENT '<comment>' ] 
+LANGUAGE <language>
+[ COMMENT '<comment>' ]
 AS $$
 BEGIN
     <procedure_body>
@@ -38,13 +38,47 @@ $$;
 This example defines a stored procedure that converts weight from kilograms (kg) to pounds (lb):
 
 ```sql
-CREATE PROCEDURE convert_kg_to_lb(kg DECIMAL(4, 2)) 
-RETURNS DECIMAL(10, 2) 
-LANGUAGE SQL 
+CREATE PROCEDURE convert_kg_to_lb(kg DECIMAL(4, 2))
+RETURNS DECIMAL(10, 2)
+LANGUAGE SQL
 COMMENT = 'Converts kilograms to pounds'
 AS $$
 BEGIN
     RETURN kg * 2.20462;
 END;
 $$;
+```
+
+You can also define a stored procedure that works with loops, conditions, and dynamic variables.
+
+```sql
+
+CREATE OR REPLACE PROCEDURE loop_test()
+RETURNS INT
+LANGUAGE SQL
+COMMENT = 'loop test'
+AS $$
+BEGIN
+    LET x RESULTSET := select number n from numbers(10);
+    LET sum := 0;
+    FOR x IN x DO
+        FOR batch in 0 TO x.n DO
+            IF batch % 2 = 0 THEN
+                sum := sum + batch;
+            ELSE
+                sum := sum - batch;
+            END IF;
+        END FOR;
+    END FOR;
+    RETURN sum;
+END;
+$$;
+```
+
+```sql
+CALL PROCEDURE loop_test();
+
+┌─Result─┐
+│   -5   │
+└────────┘
 ```

docs/en/sql-reference/20-sql-functions/03-conditional-functions/decode.md

@@ -0,0 +1,56 @@
+---
+title: DECODE
+---
+
+The DECODE function compares the select expression to each search expression in order. As soon as a search expression matches the selection expression, the corresponding result expression is returned. If no match is found and a default value is provided, the default value is returned.
+
+## Syntax
+
+```sql
+DECODE( <expr>, <search1>, <result1> [, <search2>, <result2> ... ] [, <default> ] )
+```
+
+## Arguments
+
+- `expr`: The "select expression" that is compared against each search expression. This is typically a column, but can be a subquery, literal, or other expression.
+- `searchN`: The search expressions to compare against the select expression. If a match is found, the corresponding result is returned.
+- `resultN`: The values that will be returned if the corresponding search expression matches the select expression.
+- `default`: Optional. If provided and no search expression matches, this default value is returned.
+
+## Usage Notes
+
+- Unlike `CASE`, a NULL value in the select expression matches a NULL value in the search expressions.
+- If multiple search expressions would match, only the first match's result is returned.
+
+## Examples
+
+```sql
+CREATE TABLE t (a VARCHAR);
+INSERT INTO t (a) VALUES
+    ('1'),
+    ('2'),
+    (NULL),
+    ('4');
+```
+
+Example with a default value 'other' (note that NULL equals NULL):
+
+```sql
+SELECT a, decode(a,
+                       1, 'one',
+                       2, 'two',
+                       NULL, '-NULL-',
+                       'other'
+                      ) AS decode_result
+    FROM t;
+```
+
+result:
+```
+┌─a─┬─decode_result─┐
+│ 1 │ one           │
+│ 2 │ two           │
+│   │ -NULL-        │
+│ 4 │ other         │
+└───┴───────────────┘
+```