docs: refine

docs/reference/sql/alter.md

@@ -7,31 +7,22 @@
 * Rename a table
 * Modify table options
 
-## Syntax
+## ALTER DATABASE
+
+### Syntax
 
 ```sql
 ALTER DATABASE db
    [SET <option_name>=<option_value> [, ...]
     | UNSET <option_name> [, ...]
    ]
-
-ALTER TABLE [db.]table
-   [ADD COLUMN name type [options]
-    | DROP COLUMN name
-    | MODIFY COLUMN name type
-    | MODIFY COLUMN name SET FULLTEXT [WITH <options>]
-    | MODIFY COLUMN name UNSET FULLTEXT
-    | RENAME name
-    | SET <option_name>=<option_value> [, ...]
-    | UNSET <option_name>[, ...]
-   ]
 ```
 
-## Examples
+### Examples
 
-### Modify database options
+#### Modify database options
 
-`ALTER DATABASE` statements can be used to change the options of databases.
+`ALTER DATABASE` statements can be used to modify the options of databases.
 
 Currently following options are supported:
 - `ttl`: the default retention time of data in database.
@@ -48,7 +39,26 @@ Remove the default retention time of data in the database:
 ALTER DATABASE db UNSET 'ttl';
 ```
 
-### Add column
+## ALTER TABLE
+
+### Syntax
+
+```sql
+ALTER TABLE [db.]table
+   [ADD COLUMN name type [options]
+    | DROP COLUMN name
+    | MODIFY COLUMN name type
+    | MODIFY COLUMN name SET FULLTEXT [WITH <options>]
+    | MODIFY COLUMN name UNSET FULLTEXT
+    | RENAME name
+    | SET <option_name>=<option_value> [, ...]
+    | UNSET <option_name>[, ...]
+   ]
+```
+
+### Examples
+
+#### Add column
 
 Adds a new column to the table:
 
@@ -75,7 +85,7 @@ Adds a new column as a tag(primary key) with a default value:
 ALTER TABLE monitor ADD COLUMN app STRING DEFAULT 'shop' PRIMARY KEY;
 ```
 
-### Remove column
+#### Remove column
 
 Removes a column from the table:
 
@@ -85,7 +95,7 @@ ALTER TABLE monitor DROP COLUMN load_15;
 
 The removed column can't be retrieved immediately by all subsequent queries.
 
-### Modify column type
+#### Modify column type
 
 Modify the date type of a column
 
@@ -95,7 +105,7 @@ ALTER TABLE monitor MODIFY COLUMN load_15 STRING;
 
 The modified column cannot be a tag (primary key) or time index, and it must be nullable to ensure that the data can be safely converted (returns `NULL` on cast failures).
 
-### Alter table options
+#### Alter table options
 
 `ALTER TABLE` statements can also be used to change the options of tables. 
 
@@ -130,7 +140,7 @@ ALTER TABLE monitor SET 'compaction.twcs.max_inactive_window_runs'='6';
 ALTER TABLE monitor UNSET 'ttl';
 ```
 
-### Modify column fulltext index options
+#### Modify column fulltext index options
 
 Enable fulltext index on a column:
 
@@ -155,7 +165,7 @@ The column must be a string type to alter the fulltext index.
 
 If the fulltext index has never been enabled, you can enable it and specify the `analyzer` and `case_sensitive` options. When the fulltext index is already enabled on a column, you can disable it but **cannot modify the options**.
 
-### Rename table
+#### Rename table
 
 Renames the table:
 

i18n/zh/docusaurus-plugin-content-docs/current/reference/sql/alter.md

@@ -7,14 +7,11 @@
 * 重命名表
 * 修改表选项
 
-## Syntax
+## ALTER DATABASE
 
-```sql
-ALTER DATABASE db
-   [SET <option_name>=<option_value> [, ...]
-    | UNSET <option_name> [, ...]
-   ]
+### 语法
 
+```sql
 ALTER TABLE [db.]table
    [ADD COLUMN name type [options] 
     | DROP COLUMN name
@@ -26,9 +23,9 @@ ALTER TABLE [db.]table
    ]
 ```
 
-## 示例
+### 示例
 
-### 修改数据库选项
+#### 修改数据库选项
 
 `ALTER DATABASE` 语句可以用来修改数据库的选项。
 
@@ -47,7 +44,24 @@ ALTER DATABASE db SET 'ttl'='1d';
 ALTER DATABASE db UNSET 'ttl';
 ```
 
-### 增加列
+## ALTER TABLE
+
+## 语法
+
+```sql
+ALTER TABLE [db.]table
+   [ADD COLUMN name type [options] 
+    | DROP COLUMN name
+    | MODIFY COLUMN name type
+    | MODIFY COLUMN name SET FULLTEXT [WITH <options>]
+    | RENAME name
+    | SET <option_name>=<option_value> [, ...]
+   ]
+```
+
+### 示例
+
+#### 增加列
 
 在表中增加新列：
 
@@ -75,7 +89,7 @@ ALTER TABLE monitor ADD COLUMN app STRING DEFAULT 'shop' PRIMARY KEY;
 ```
 
 
-### 移除列
+#### 移除列
 
 从表中移除列：
 
@@ -85,7 +99,7 @@ ALTER TABLE monitor DROP COLUMN load_15;
 
 后续的所有查询立刻不能获取到被移除的列。
 
-### 修改列类型
+#### 修改列类型
 
 修改列的数据类型
 
@@ -95,7 +109,7 @@ ALTER TABLE monitor MODIFY COLUMN load_15 STRING;
 
 被修改的的列不能是 tag 列（primary key）或 time index 列，同时该列必须允许空值 `NULL` 存在来保证数据能够安全地进行转换（转换失败时返回 `NULL`）。
 
-### 修改表的参数
+#### 修改表的参数
 
 `ALTER TABLE` 语句也可以用来更改表的选项。
 当前支持修改以下表选项：
@@ -130,8 +144,7 @@ ALTER TABLE monitor SET 'compaction.twcs.max_inactive_window_runs'='6';
 ALTER TABLE monitor UNSET 'ttl';
 ```
 
-
-### 修改列全文索引选项
+#### 修改列全文索引选项
 
 启用列的全文索引：
 
@@ -156,7 +169,7 @@ ALTER TABLE monitor MODIFY COLUMN load_15 UNSET FULLTEXT;
 
 当列的全文索引未开启过时，可以启用全文索引，并设置 `analyzer` 和 `case_sensitive` 选项；当列的全文索引选项已经启用时，可以关闭全文索引，**但不能修改选项**。
 
-### 重命名表
+#### 重命名表
 
 ```sql
 ALTER TABLE monitor RENAME monitor_new;