From 2658da451c417d03119cb9fe263a9fd0e8dcaa96 Mon Sep 17 00:00:00 2001
From: Elias Soong <elias.soong@gmail.com>
Date: Wed, 14 Apr 2021 16:43:45 +0800
Subject: [PATCH] [TD-2577] <docs>: "GROUP BY" add "HAVING" support.

---
 documentation20/cn/11.administrator/docs.md |  4 ++--
 documentation20/cn/12.taos-sql/docs.md      | 15 ++++++++++++---
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/documentation20/cn/11.administrator/docs.md b/documentation20/cn/11.administrator/docs.md
index 961a3801e7..5eccc67ff8 100644
--- a/documentation20/cn/11.administrator/docs.md
+++ b/documentation20/cn/11.administrator/docs.md
@@ -463,7 +463,7 @@ TDengine的所有可执行文件默认存放在 _/usr/local/taos/bin_ 目录下
 
 | 关键字列表 |             |              |            |           |
 | ---------- | ----------- | ------------ | ---------- | --------- |
-| ABLOCKS    | CONNECTIONS | GT           | MNODES     | SLIDING   |
+| ABLOCKS    | CONNECTIONS | HAVING       | MNODES     | SLIDING   |
 | ABORT      | COPY        | ID           | MODULES    | SLIMIT    |
 | ACCOUNT    | COUNT       | IF           | NCHAR      | SMALLINT  |
 | ACCOUNTS   | CREATE      | IGNORE       | NE         | SPREAD    |
@@ -499,5 +499,5 @@ TDengine的所有可执行文件默认存放在 _/usr/local/taos/bin_ 目录下
 | CONCAT     | GLOB        | METRICS      | SET        | VIEW      |
 | CONFIGS    | GRANTS      | MIN          | SHOW       | WAVG      |
 | CONFLICT   | GROUP       | MINUS        | SLASH      | WHERE     |
-| CONNECTION |             |              |            |           |
+| CONNECTION | GT          |              |            |           |
 
diff --git a/documentation20/cn/12.taos-sql/docs.md b/documentation20/cn/12.taos-sql/docs.md
index 864169b898..b6d81720cf 100644
--- a/documentation20/cn/12.taos-sql/docs.md
+++ b/documentation20/cn/12.taos-sql/docs.md
@@ -407,10 +407,10 @@ SELECT select_expr [, select_expr ...]
     [INTERVAL (interval_val [, interval_offset])]
     [SLIDING sliding_val]
     [FILL fill_val]
-    [GROUP BY col_list]
+    [GROUP BY col_list [HAVING having_condition]]
     [ORDER BY col_list { DESC | ASC }]
-    [SLIMIT limit_val [, SOFFSET offset_val]]
-    [LIMIT limit_val [, OFFSET offset_val]]
+    [SLIMIT limit_val [SOFFSET offset_val]]
+    [LIMIT limit_val [OFFSET offset_val]]
     [>> export_file];
 ```
 
@@ -648,6 +648,15 @@ Query OK, 1 row(s) in set (0.001091s)
 2. 针对单一字段的过滤，如果是时间过滤条件，则一条语句中只支持设定一个；但针对其他的（普通）列或标签列，则可以使用 `OR` 关键字进行组合条件的查询过滤。例如：((value > 20 AND value < 30) OR (value < 12)) 。
 3. 从 2.0.17 版本开始，条件过滤开始支持 BETWEEN AND 语法，例如 `WHERE col2 BETWEEN 1.5 AND 3.25` 表示查询条件为“1.5 ≤ col2 ≤ 3.25”。
 
+### GROUP BY 之后的 HAVING 过滤
+
+从 2.0.20 版本开始，GROUP BY 之后允许再跟一个 HAVING 子句，对成组后的各组数据再做筛选。HAVING 子句可以使用聚合函数和选择函数作为过滤条件（但暂时不支持 LEASTSQUARES、TOP、BOTTOM、LAST_ROW）。
+
+例如，如下语句只会输出 `AVG(f1) > 0` 的分组：
+```mysql
+SELECT AVG(f1), SPREAD(f1, f2, st2.f1) FROM st2 WHERE f1 > 0 GROUP BY f1 HAVING AVG(f1) > 0;
+```
+
 ### SQL 示例 
 
 - 对于下面的例子，表tb1用以下语句创建
-- 
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