chore: doc about add_months and column comment (#2449)

Author: TCeason

docs/en/sql-reference/10-sql-commands/00-ddl/01-table/90-alter-table-column.md

@@ -4,7 +4,7 @@ sidebar_position: 4
 ---
 import FunctionDescription from '@site/src/components/FunctionDescription';
 
-<FunctionDescription description="Introduced or updated: v1.2.415"/>
+<FunctionDescription description="Introduced or updated: v1.2.760"/>
 
 import EEFeature from '@site/src/components/EEFeature';
 
@@ -35,13 +35,18 @@ MODIFY [ COLUMN ] <column_name> DROP STORED
 ALTER TABLE [ IF EXISTS ] [ <database_name>. ]<table_name>
 RENAME [ COLUMN ] <column_name> TO <new_column_name>
 
--- Change data type and/or comment
--- If you only want to modify or add a comment for a column, you must still specify the current data type for that column in the command
+-- Change data type
 ALTER TABLE [ IF EXISTS ] [ <database_name>. ]<table_name> 
-MODIFY [ COLUMN ] <column_name> <new_data_type> [ DEFAULT <constant_value> ] [ COMMENT '<comment>' ]
-       [ , [ COLUMN ] <column_name> <new_data_type> [ DEFAULT <constant_value> ] [ COMMENT '<comment>' ] ]
+MODIFY [ COLUMN ] <column_name> <new_data_type> [ DEFAULT <constant_value> ]
+       [ , [ COLUMN ] <column_name> <new_data_type> [ DEFAULT <constant_value> ] ]
        ...
 
+-- Change comment
+ALTER TABLE [ IF EXISTS ] [ <database_name>. ]<table_name>
+MODIFY [ COLUMN ] <column_name> [ COMMENT '<comment>' ]
+[ , [ COLUMN ] <column_name> [ COMMENT '<comment>' ] ]
+...
+    
 -- Set / Unset masking policy for a column
 ALTER TABLE [ IF EXISTS ] [ <database_name>. ]<table_name>
 MODIFY [ COLUMN ] <column_name> SET MASKING POLICY <policy_name>
@@ -218,7 +223,7 @@ SHOW CREATE TABLE students_info;
 └───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
 
 -- Add a comment to the 'age' column
-ALTER TABLE students_info MODIFY COLUMN age VARCHAR(10) COMMENT 'abc';
+ALTER TABLE students_info MODIFY COLUMN age COMMENT 'abc';
 
 SHOW CREATE TABLE students_info;
 

docs/en/sql-reference/20-sql-functions/05-datetime-functions/add-months.md

@@ -0,0 +1,90 @@
+---
+title: ADD_MONTHS
+---
+import FunctionDescription from '@site/src/components/FunctionDescription';
+
+<FunctionDescription description="Introduced or updated: v1.2.760"/>
+
+The add_months() function adds a specified number of months to a given date or timestamp.
+
+If the input date is month-end or exceeds the resulting month’s days, the result is adjusted to the last day of the new month. Otherwise, the original day is preserved.
+
+## Syntax
+
+```sql
+ADD_MONTHS(<date_or_timestamp>, <number_of_months>)
+```
+
+| Parameter            | Description                                                                 |
+|----------------------|-----------------------------------------------------------------------------|
+| `<date_or_timestamp>` | The starting date or timestamp to which months will be added               |
+| `<number_of_months>`  | The integer number of months to add (can be negative to subtract months)   |
+
+## Return Type
+
+Returns a TIMESTAMP or DATE type
+
+## Examples
+
+### Basic Month Addition
+```sql
+SELECT ADD_MONTHS('2023-01-15'::DATE, 3);
+├───────────────────────────────────┤
+│ 2023-04-15                        │
+╰───────────────────────────────────╯
+```
+
+### Subtracting Months
+```sql
+SELECT ADD_MONTHS('2023-06-20'::DATE, -4);
+├─────────────────────────────────────┤
+│ 2023-02-20                          │
+╰─────────────────────────────────────╯
+```
+
+### Month-End Adjustment
+```sql
+SELECT ADD_MONTHS('2023-01-31'::DATE, 1);
+├───────────────────────────────────┤
+│ 2023-02-28                        │
+╰───────────────────────────────────╯
+```
+
+### With Timestamp Preservation
+```sql
+SELECT ADD_MONTHS('2023-03-15 14:30:00'::TIMESTAMP, 5);
+├─────────────────────────────────────────────────┤
+│ 2023-08-15 14:30:00.000000                      │
+╰─────────────────────────────────────────────────╯
+```
+
+### With last day of month
+```sql
+CREATE TABLE contracts (
+    id INT,
+    sign_date DATE,
+    duration_months INT
+);
+
+INSERT INTO contracts VALUES
+    (1, '2023-01-15', 12),
+    (2, '2024-02-28', 6),
+    (3, '2023-11-30', 3);
+
+SELECT 
+    id,
+    sign_date,
+    ADD_MONTHS(sign_date, duration_months) AS end_date
+FROM contracts;
+├─────────────────┼────────────────┼────────────────┤
+│               1 │ 2023-01-15     │ 2024-01-15     │
+│               2 │ 2024-02-28     │ 2024-08-28     │
+│               3 │ 2023-11-30     │ 2024-02-29     │
+╰───────────────────────────────────────────────────╯
+
+```
+
+## See Also
+
+- [DATE_ADD](date-add.md): Alternative function for adding specific time intervals
+- [DATE_SUB](date-sub.md): Function for subtracting time intervals

docs/en/sql-reference/20-sql-functions/05-datetime-functions/date-add.md

@@ -90,3 +90,8 @@ SELECT DATE_ADD(month, 1, '2023-02-28'::DATE);
 ╰────────────────────────────────────────╯
 
 ```
+
+## See Also
+
+- [ADD_MONTH](add-months.md): Function for add months
+- [DATE_SUB](date-sub.md): Function for subtracting time intervals

docs/en/sql-reference/20-sql-functions/05-datetime-functions/index.md

@@ -56,6 +56,7 @@ This page provides a comprehensive overview of Date & Time functions in Databend
 | [MONTHS_BETWEEN](months-between.md)      | Returns the number of months between two dates                                               | `MONTHS_BETWEEN('2024-06-04', '2024-01-04')` → `5`                                   |
 | [DATE_BETWEEN](date-between.md)          | Checks if a date is between two other dates                                                  | `DATE_BETWEEN('2024-06-04', '2024-06-01', '2024-06-10')` → `true`                    |
 | [AGE](age.md)                            | Calculate the difference between timestamps or between a timestamp and the current date/time | `AGE('2000-01-01'::TIMESTAMP, '1990-05-15'::TIMESTAMP)` → `9 years 7 months 17 days` |
+| [ADD_MONTHS](add-months.md)              | Adds months to a date while preserving end-of-month days.                                    | `ADD_MONTHS('2025-04-30',1)` → `2025-05-31`                                          |
 
 ## Date & Time Truncation Functions