How to Use the Command 'mongoexport' (with Examples)

Mongoexport is a command-line tool provided by MongoDB that allows users to export data from a MongoDB instance into more universal file formats, such as JSON or CSV. This can be particularly useful for data backup, data sharing between different database systems, and straightforward data manipulation outside of MongoDB environments. As part of the broader MongoDB Database Tools suite, mongoexport can vastly enhance your data portability and utilization capabilities.

Use Case 1: Export a Collection to stdout, Formatted as JSON

Code:

mongoexport --uri=connection_string --collection=collection_name

Motivation:

You may want to quickly check the raw data in a MongoDB collection in its JSON format. By exporting to stdout, you can inspect the data directly in your terminal without creating intermediate files. This is particularly useful for quick debugging or data review.

Explanation:

• --uri=connection_string: Specifies the connection string needed to connect to the MongoDB instance. The connection string usually includes the hostname, port number, and any authentication information required to connect.
• --collection=collection_name: The name of the collection you wish to export data from.

Example Output:

When executed, this command prints the collection documents directly in the terminal window, each formatted as a JSON document, allowing for a rapid inspection of the data stored.

Use Case 2: Export Documents That Match a Query to a JSON File

Code:

mongoexport --db=database_name --collection=collection_name --query="query_object" --out=path/to/file.json

Motivation:

Sometimes you need to export only a subset of the data from a MongoDB collection based on a specific condition. This might be necessary if the entire data set is too large or irrelevant for the task at hand. Using a query filter streamlines the data export by allowing you to extract only pertinent information.

Explanation:

• --db=database_name: Specifies the database containing the desired collection.
• --collection=collection_name: Indicates the particular collection you want to export data from.
• --query="query_object": Defines the query criteria as a JSON object. It filters the documents in the collection according to the specified parameters.
• --out=path/to/file.json: Determines the output file path where the exported JSON data will be stored.

Example Output:

Running this command exports only those documents that meet the query criteria, saving them in a JSON file. The output file can then be easily shared or used for further analysis.

Use Case 3: Export Documents as a JSON Array

Code:

mongoexport --collection=collection_name --jsonArray

Motivation:

Exporting documents as a JSON array is crucial when you want the data to be directly usable within JSON-compatible applications or scripts. This format eases data integration processes by packaging multiple documents in a single, structured JSON array.

Explanation:

• --collection=collection_name: Identifies the collection to export from.
• --jsonArray: Specifies that the output should be formatted as a JSON array rather than having each document on a new line.

Example Output:

The command outputs the entire collection wrapped as an array of JSON objects, making it ready for use with applications that require this specific data structure.

Use Case 4: Export Documents to a CSV File

Code:

mongoexport --collection=collection_name --type=csv --fields="field1,field2,..." --out=path/to/file.csv

Motivation:

CSV files are widely used because of their simplicity and compatibility with spreadsheet programs like Excel. Exporting MongoDB documents to CSV allows data to be easily analyzed or presented in a tabular format.

Explanation:

• --collection=collection_name: Selects the collection for exporting data.
• --type=csv: Instructs mongoexport to format the output as CSV.
• --fields="field1,field2,...": Lists specific fields to include in the export, ensuring only necessary data is included.
• --out=path/to/file.csv: Designates the file path where the CSV output should be saved.

Example Output:

The resulting CSV file contains the specified fields from each document in a columnar format, facilitating analysis or presentation in spreadsheet tools.

Use Case 5: Export Documents Matching a Query File to CSV, Omitting the Header

Code:

mongoexport --collection=collection_name --type=csv --fields="field1,field2,..." --queryFile=path/to/file --noHeaderLine --out=path/to/file.csv

Motivation:

For automated processes or subsequent scripts, omitting the header line from a CSV file may be necessary. If you repeatedly run exports with known fields, you may not require headers, simplifying data handling in each cycle.

Explanation:

• --collection=collection_name: Specifies the targeted collection.
• --type=csv: Outputs in CSV format.
• --fields="field1,field2,...": Lists the fields to include.
• --queryFile=path/to/file: Provides a path to a file containing the query criteria.
• --noHeaderLine: Ensures that no header is included in the CSV output.
• --out=path/to/file.csv: Points to the file location to save the CSV export.

Example Output:

This results in a CSV file containing only the filtered data rows, making it ideal for batch processing or automated workflows where headers are unnecessary.

Use Case 6: Export Documents to stdout, Formatted as Human-Readable JSON

Code:

mongoexport --uri=mongodb_uri --collection=collection_name --pretty

Motivation:

Sometimes readability matters more than compactness. Exporting with the --pretty option produces a formatted output that’s much more approachable for manual review, debugging, or presentation purposes.

Explanation:

• --uri=mongodb_uri: Specifies the MongoDB instance connection string.
• --collection=collection_name: Selects the collection to export from.
• --pretty: Formats the output JSON in a human-readable way, with indentation and line breaks.

Example Output:

The exported data is displayed with clear indentation and formatting, making it easier for humans to read and interpret compared to a single-line JSON.

Use Case 7: Display Help

Code:

mongoexport --help

Motivation:

It’s always helpful to access the tool’s manual, especially when you want to confirm syntax or explore additional options. The help command provides immediate access to a comprehensive list of available commands and their explanations, ensuring efficient and informed use of mongoexport.

Explanation:

• --help: Displays all available options and flags for the mongoexport command, along with descriptions and usage examples.

Example Output:

Executing this command brings up a detailed guide in the terminal, containing usage rules, argument descriptions, and examples for using mongoexport effectively.

Conclusion:

Understanding how to leverage the mongoexport command can significantly enhance your ability to manage and migrate data across systems. From simple exports for quick viewing to detailed and formatted outputs for integration with other tools, mongoexport offers versatility and depth. Whether configured for JSON inspection or CSV analysis, mastering these use cases can streamline your data workflows and improve your data handling efficiency.