Add page for timestamp

mint.json

@@ -800,6 +800,7 @@
                 "sql/data-types/map-type",
                 "sql/data-types/jsonb",
                 "sql/data-types/rw-int256",
+                "sql/data-types/timestamp",
                 "sql/data-types/supported-protobuf-types"
               ]
             },

sql/data-types/timestamp.mdx

@@ -0,0 +1,56 @@
+---
+title: "Timestamp"
+sidebarTitle: Timestamp type
+description: "Use the timestamp data type to handle date and time information."
+---
+
+Timestamp data types are used to store and process precise time information. RisingWave supports two types of timestamps:
+
+- `timestamp`: Stores date and time values without timezone, supporting up to **nanosecond** precision (9 digits after the decimal point).
+
+- `timestamptz`: Stores date and time values along with time zone information, supporting up to **microsecond** precision (6 digits after the decimal point).
+
+
+## Precision preservation
+
+<Note>
+Added in version 2.1.
+</Note>
+
+Nanosecond precision is fully maintained for `timestamp` during the following operations:
+
+- Reading from or writing to external sources (Kafka, Iceberg, Parquet, etc.) preserves nanoseconds automatically.
+
+- Adding or subtracting an interval from a timestamp.
+
+    ```sql Add an interval
+    SELECT '2022-03-13 01:00:00.123456789'::timestamp + INTERVAL '24' HOUR;
+    -- Result: 2022-03-14 01:00:00.123456789
+    ```
+
+    ```sql Subtract an interval
+    SELECT '2022-03-14 01:00:00.123456789'::timestamp - INTERVAL '24' HOUR;
+    -- Result: 2022-03-13 01:00:00.123456789
+    ```
+
+## Precision loss
+
+Nanosecond precision is lost (truncated to microseconds or discarded) under the following scenarios:
+
+- Converting timestamp to types with lower precision:
+    - timestamptz
+    - time
+    - date
+
+- Subtracting Timestamps (timestamp - timestamp): The result is an interval, which only has microsecond precision.
+    ```sql Subtract two timestamps
+    SELECT '2022-03-13 03:00:00.123456789'::timestamp - '2022-03-13 01:00:00.000000000'::timestamp;
+    -- Result: 02:00:00.123456 (Note that nanosecond precision is truncated.)
+    ```
+
+## Related topic
+
+For more functions and usage on timestamp, see [Date and time functions and operators](/sql/functions/datetime).
+
+
+