Merge pull request #7498 from taosdata/docs/Update-Latest-Feature

[TD-4555] <docs>: update example code about SQL function DERIVATIVE().

documentation20/cn/12.taos-sql/docs.md

@@ -1287,15 +1287,15 @@ TDengine支持针对数据的聚合查询。提供支持的聚合和选择函数
 
     示例：
     ```mysql
-    taos> select derivative(current, 1d, 0) from t1;
-               ts            | derivative(current, 1d, 0) |
-    =======================================================
-     2021-08-20 09:18:44.032 |              119.999966667 |
-     2021-08-20 10:18:44.032 |              -48.000000000 |
-     2021-08-20 11:18:44.032 |              -48.000000000 |
-     2021-08-20 12:18:44.033 |              215.999940000 |
-     2021-08-20 13:18:44.034 |             -167.999953333 |
-    Query OK, 5 row(s) in set (0.004772s)
+    taos> select derivative(current, 10m, 0) from t1;
+               ts            | derivative(current, 10m, 0) |
+    ========================================================
+     2021-08-20 10:11:22.790 |                 0.500000000 |
+     2021-08-20 11:11:22.791 |                 0.166666620 |
+     2021-08-20 12:11:22.791 |                 0.000000000 |
+     2021-08-20 13:11:22.792 |                 0.166666620 |
+     2021-08-20 14:11:22.792 |                -0.666666667 |
+    Query OK, 5 row(s) in set (0.004883s)
     ```
 
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