Database management and table management in English

src/UserGuide/Master/Table/Basic-Concept/Database-Management.md

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+
+# Database Management
+
+## 1. Database Management
+
+### 1.1 Create a Database
+
+This command is used to create a database.
+
+**Syntax:**
+
+```SQL
+ CREATE DATABASE (IF NOT EXISTS)? <DATABASE_NAME> (WITH properties)?
+```
+
+**Note: **
+
+1. `<DATABASE_NAME>`: The name of the database, with the following characteristics:
+  - Case-insensitive.
+  - Can include commas (`,`), underscores (`_`), numbers, letters, and Chinese characters.
+  - Maximum length is 64 characters.
+  - Names with special characters or Chinese characters must be enclosed in double quotes (`""`).
+
+2. `WITH properties`: Property names are case-insensitive and currently cannot be modified. For more details, refer to the case sensitivity rules [case-sensitivity](../SQL-Manual/Identifier.md#2-case-sensitivity)。Configurable properties include:
+
+| Property                | Description                                                  | Default Value        |
+| ----------------------- | ------------------------------------------------------------ | -------------------- |
+| TTL                     | Automatic data expiration time, in milliseconds              | `INF`                |
+| TIME_PARTITION_INTERVAL | Time partition interval for the database, in milliseconds    | `604800000` (7 days) |
+| SCHEMA_REGION_GROUP_NUM | Number of metadata replica groups; generally does not require modification | `1`                  |
+| DATA_REGION_GROUP_NUM   | Number of data replica groups; generally does not require modification | `2`                  |
+
+**Examples:**
+
+```SQL
+CREATE DATABASE database1;
+CREATE DATABASE IF NOT EXISTS database1;
+
+// Sets TTL to 1 year.
+CREATE DATABASE IF NOT EXISTS database1 with(TTL=31536000000)；
+```
+
+### 1.2 Use a Database
+
+Specify the current database as the namespace for table operations.
+
+**Syntax:**
+
+```SQL
+USE <DATABASE_NAME>
+```
+
+**Example:** 
+
+```SQL
+USE database1
+```
+
+### 1.3 View the Current Database
+
+Displays the name of the currently connected database. If no USE statement has been executed, the default is `null`.
+
+**Syntax:**
+
+```SQL
+SHOW CURRENT_DATABASE
+```
+
+**Example:**
+
+```SQL
+IoTDB> SHOW CURRENT_DATABASE;
++---------------+
+|CurrentDatabase|
++---------------+
+|           null|
++---------------+
+
+IoTDB> USE test;
+
+IoTDB> SHOW CURRENT_DATABASE;
++---------------+
+|CurrentDatabase|
++---------------+
+|   iot_database|
++---------------+
+```
+
+### 1.4 View All Databases
+
+Displays all databases and their properties.
+
+**Syntax:**
+
+```SQL
+SHOW DATABASES (DETAILS)?
+```
+
+**Columns Explained:**
+
+
+| Column Name             | Description                                                  |
+| ----------------------- | ------------------------------------------------------------ |
+| database                | Name of the database.                                        |
+| TTL                     | Data retention period. If TTL is specified when creating a database, it applies to all tables within the database. You can also set or update the TTL of individual tables using [create table](../Basic-Concept/Table-Management.md#11-create-a-table) 、[alter table](../Basic-Concept/Table-Management.md#14-update-tables) . |
+| SchemaReplicationFactor | Number of metadata replicas, ensuring metadata high availability. This can be configured in the `iotdb-system.properties` file under the `schema_replication_factor` property. |
+| DataReplicationFactor   | Number of data replicas, ensuring data high availability. This can be configured in the `iotdb-system.properties` file under the `data_replication_factor` property. |
+| TimePartitionInterval   | Time partition interval, determining how often data is grouped into directories on disk. The default is typically one week. |
+| Model                   | Returned when using the `DETAILS` option, showing the data model corresponding to each database (e.g., timeseries tree model or device table model). |
+
+**Examples:** 
+
+```SQL
+IoTDB> show databases
++---------+-------+-----------------------+---------------------+---------------------+
+| Database|TTL(ms)|SchemaReplicationFactor|DataReplicationFactor|TimePartitionInterval|
++---------+-------+-----------------------+---------------------+---------------------+
+|test_prop|    300|                      3|                    2|               100000|
+|    test2|    300|                      3|                    2|            604800000|
++---------+-------+-----------------------+---------------------+---------------------+
+IoTDB> show databases details
++---------+-------+-----------------------+---------------------+---------------------+-----------------------+-----------------------+
+| Database|TTL(ms)|SchemaReplicationFactor|DataReplicationFactor|TimePartitionInterval|SchemaRegionGroupNum|  DataRegionGroupNum|
++---------+-------+-----------------------+---------------------+---------------------+-----------------------+-----------------------+
+|test_prop|    300|                      3|                    2|               100000|                      1|                      2|
+|    test2|    300|                      3|                    2|            604800000|                      1|                      2|
++---------+-------+-----------------------+---------------------+---------------------+-----------------------+-----------------------+
+```
+
+### 1.5 Update a Database
+
+Currently not supported; will be available after version 2.0.2.1.
+
+### 1.6 Delete a Database
+
+Deletes the specified database and all associated tables and data.
+
+**Syntax:**
+
+```SQL
+DROP DATABASE (IF EXISTS)? <DATABASE_NAME>
+```
+
+**Note:**
+
+1. A database currently in use can still be dropped.
+2. Deleting a database removes all its tables and stored data.
+
+**Example:**
+
+```SQL
+DROP DATABASE IF EXISTS database1
+```