add notice for now usage in stale read (#13480)

pingcap · May 9, 2023 · 3dc08ee · 3dc08ee
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commit 3dc08ee
Showing 1 changed file with 1 addition and 1 deletion.
diff --git a/develop/dev-guide-use-stale-read.md b/develop/dev-guide-use-stale-read.md
@@ -100,7 +100,7 @@ In addition to specifying an exact time, you can also specify the following:
 - `AS OF TIMESTAMP TIDB_BOUNDED_STALENESS('2016-10-08 16:45:26', '2016-10-08 16:45:29')` queries the latest data between `2016-10-08 16:45:26` and `2016-10-08 16:45:29`.
 - `AS OF TIMESTAMP TIDB_BOUNDED_STALENESS(NOW() -INTERVAL 20 SECOND, NOW())` queries the latest data within 20 seconds.
 
-Note that the specified timestamp or interval cannot be too early or later than the current time.
+Note that the specified timestamp or interval cannot be too early or later than the current time. Additionally, `NOW()` defaults to second precision. To achieve higher precision, you can add a parameter, such as using `NOW(3)` for millisecond precision. For more information, see [MySQL documentation](https://dev.mysql.com/doc/refman/5.7/en/date-and-time-functions.html#function_now).
 
 Expired data will be recycled by [Garbage Collection](/garbage-collection-overview.md) in TiDB, and the data will be retained for a short period before being cleared. The period is called [GC Life Time (default 10 minutes)](/system-variables.md#tidb_gc_life_time-new-in-v50). When a GC starts, the current time minus the time period will be used as the **GC Safe Point**. If you try to read the data before GC Safe Point, TiDB will report the following error: