src/UserGuide/Master/Table/Tools-System/Schema-Export-Tool_timecho.md

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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                                                               | No                                  | `TimechoDB@2021`(Before V2.0.6 it is 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                                  |                                               |

### 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
);
```