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# Schema Export

## 1. Overview

The schema export tool `export-schema.sh/bat` is located in the `tools` directory. It can export schema from a specified database in IoTDB to a script file.

## 2. Detailed Functionality

### 2.1 Parameter

| **Short Param** | **Full Param**           | **Description**                                                          | Required                            | Default                                     |
|-----------------|--------------------------|--------------------------------------------------------------------------| ------------------------------------- |---------------------------------------------|
| `-h`            | `-- host`                | Hostname                                                                 | No                                  | 127.0.0.1                                   |
| `-p`            | `--port`                 | Port number                                                              | No                                  | 6667                                        |
| `-u`            | `--username`             | Username                                                                 | No                                  | root                                        |
| `-pw`           | `--password`             | Password. Supported for hidden input since V2.0.9-beta                                                                | No                                  | root    |
| `-sql_dialect`  | `--sql_dialect`          | Specifies whether the server uses`tree `model or`table `model            | No                                 | tree                                        |
| `-db`           | `--database`             | Target database to export (only applies when`-sql_dialect=table`)        | Required if`-sql_dialect=table` | -                                           |
| `-table`        | `--table`                | Target table to export (only applies when`-sql_dialect=table`)           | No                                 | -                                           |
| `-t`            | `--target`               | Output directory (created if it doesn't exist)                           | Yes                                 |                                             |
| `-path`         | `--path_pattern`         | Path pattern for metadata export                                         | Required if`-sql_dialect=tree`  |                                             |
| `-pfn`          | `--prefix_file_name`     | Output filename prefix                                                   | No                                  | `dump_dbname.sql`                           |
| `-lpf`          | `--lines_per_file`       | Maximum lines per dump file (only applies when`-sql_dialect=tree`)       | No                                 | `10000`                                     |
| `-timeout`      | `--query_timeout`        | Query timeout in milliseconds (`-1`= no timeout)                         | No                                  | -1Range：`-1 to Long. max=9223372036854775807` |
| `-help`         | `--help`                 | Display help information                                                 | No                                  |                                             |
| `-usessl`       | `--use_ssl`              | Use SSL protocol. Supported since V2.0.9-beta                            | No      | -                                    |
| `-ts`           | `--trust_store`          | Trust store. Supports hidden input. Supported since V2.0.9-beta          | No      | -                                    |
| `-tpw`          | `--trust_store_password` | Trust store password. Supports hidden input. Supported since V2.0.9-beta | No        | -                                    |

### 2.2 Command

```Bash
Shell
# Unix/OS X
> tools/export-schema.sh [-sql_dialect<sql_dialect>] -db<database> -table<table>  
                [-h <host>] [-p <port>] [-u <username>] [-pw <password>] 
                -t <target_directory> [-path <exportPathPattern>] [-pfn <prefix_file_name>] 
                [-lpf <lines_per_file>] [-timeout <query_timeout>]
# Windows
# Before version V2.0.4.x
> tools\export-schema.bat [-sql_dialect<sql_dialect>] -db<database> -table<table>  
                [-h <host>] [-p <port>] [-u <username>] [-pw <password>] 
                -t <target_directory> [-path <exportPathPattern>] [-pfn <prefix_file_name>] 
                [-lpf <lines_per_file>] [-timeout <query_timeout>]
                
# V2.0.4.x and later versions
> tools\windows\schema\export-schema.bat [-sql_dialect<sql_dialect>] -db<database> -table<table>  
                [-h <host>] [-p <port>] [-u <username>] [-pw <password>] 
                -t <target_directory> [-path <exportPathPattern>] [-pfn <prefix_file_name>] 
                [-lpf <lines_per_file>] [-timeout <query_timeout>]
```

### 2.3 Examples

Export schema from `database1` to `/home`:

```Bash
./export-schema.sh -sql_dialect table -t /home/ -db database1
```

Output `dump_database1.sql`：

```sql
DROP TABLE IF EXISTS table1;
CREATE TABLE table1(
        time TIMESTAMP TIME,
        region STRING TAG,
        plant_id STRING TAG,
        device_id STRING TAG,
        model_id STRING ATTRIBUTE,
        maintenance STRING ATTRIBUTE,
        temperature FLOAT FIELD,
        humidity FLOAT FIELD,
        status BOOLEAN FIELD,
        arrival_time TIMESTAMP FIELD
);
DROP TABLE IF EXISTS table2;
CREATE TABLE table2(
        time TIMESTAMP TIME,
        region STRING TAG,
        plant_id STRING TAG,
        device_id STRING TAG,
        model_id STRING ATTRIBUTE,
        maintenance STRING ATTRIBUTE,
        temperature FLOAT FIELD,
        humidity FLOAT FIELD,
        status BOOLEAN FIELD,
        arrival_time TIMESTAMP FIELD
);
```