docs: show user|system databases and show normal|child tables

docs/en/12-taos-sql/16-operators.md

@@ -54,6 +54,7 @@ LIKE is used together with wildcards to match strings. Its usage is described as
 MATCH and NMATCH are used together with regular expressions to match strings. Their usage is described as follows:
 
 - Use POSIX regular expression syntax. For more information, see Regular Expressions.
+- The `MATCH` operator returns true when the regular expression is matched. The `NMATCH` operator returns true when the regular expression is not matched.
 - Regular expression can be used against only table names, i.e. `tbname`, and tags/columns of binary/nchar types.
 - The maximum length of regular expression string is 128 bytes. Configuration parameter `maxRegexStringLen` can be used to set the maximum allowed regular expression. It's a configuration parameter on the client side, and will take effect after restarting the client.
 

docs/en/12-taos-sql/24-show.md

@@ -73,10 +73,10 @@ Shows the SQL statement used to create the specified table. This statement can b
 ## SHOW DATABASES
 
 ```sql
-SHOW DATABASES;
+SHOW [USER | SYSTEM] DATABASES;
 ```
 
-Shows all user-created databases.
+Shows all databases. The `USER` qualifier specifies only user-created databases. The `SYSTEM` qualifier specifies only system databases.
 
 ## SHOW DNODES
 
@@ -183,10 +183,10 @@ Shows all subscriptions in the system.
 ## SHOW TABLES
 
 ```sql
-SHOW [db_name.]TABLES [LIKE 'pattern'];
+SHOW [NORMAL | CHILD] [db_name.]TABLES [LIKE 'pattern'];
 ```
 
-Shows all standard tables and subtables in the current database. You can use LIKE for fuzzy matching.
+Shows all standard tables and subtables in the current database. You can use LIKE for fuzzy matching. The `Normal` qualifier specifies standard tables. The `CHILD` qualifier specifies subtables.
 
 ## SHOW TABLE DISTRIBUTED
 

docs/zh/12-taos-sql/16-operators.md

@@ -54,6 +54,7 @@ LIKE 条件使用通配符字符串进行匹配检查，规则如下：
 MATCH 条件和 NMATCH 条件使用正则表达式进行匹配，规则如下：
 
 - 支持符合 POSIX 规范的正则表达式，具体规范内容可参见 Regular Expressions。
+- MATCH 和正则表达式匹配时, 返回 TURE.  NMATCH 和正则表达式不匹配时, 返回 TRUE. 
 - 只能针对子表名（即 tbname）、字符串类型的标签值进行正则表达式过滤，不支持普通列的过滤。
 - 正则匹配字符串长度不能超过 128 字节。可以通过参数 maxRegexStringLen 设置和调整最大允许的正则匹配字符串，该参数是客户端配置参数，需要重启客户端才能生效
 

docs/zh/12-taos-sql/24-show.md

@@ -73,10 +73,10 @@ SHOW CREATE TABLE [db_name.]tb_name
 ## SHOW DATABASES
 
 ```sql
-SHOW DATABASES;
+SHOW [USER | SYSTEM] DATABASES;
 ```
 
-显示用户定义的所有数据库。
+显示定义的所有数据库。SYSTEM 指定只显示系统数据库。USER 指定只显示用户创建的数据库。
 
 ## SHOW DNODES
 
@@ -183,10 +183,10 @@ SHOW SUBSCRIPTIONS;
 ## SHOW TABLES
 
 ```sql
-SHOW [db_name.]TABLES [LIKE 'pattern'];
+SHOW [NORMAL | CHILD] [db_name.]TABLES [LIKE 'pattern'];
 ```
 
-显示当前数据库下的所有普通表和子表的信息。可以使用 LIKE 对表名进行模糊匹配。
+显示当前数据库下的所有普通表和子表的信息。可以使用 LIKE 对表名进行模糊匹配。NORMAL 指定只显示普通表信息， CHILD 指定只显示子表信息。
 
 ## SHOW TABLE DISTRIBUTED