How to export collection to CSV in MongoDB?

问题

How do you export all the records in a MongoDB collection to a .csv file?

mongoexport --host localhost --db dbname --collection name --type=csv > test.csv

This asks me to specify name of the fields I need to export. Can I just export all the fields without specifying the names of fields?

回答1:

@karoly-horvath has it right. Fields are required for csv.

According to this bug in the MongoDB issue tracker https://jira.mongodb.org/browse/SERVER-4224 you MUST provide the fields when exporting to a csv. The docs are not clear on it. That is the reason for the error.

Try this:

mongoexport --host localhost --db dbname --collection name --csv --out text.csv --fields firstName,middleName,lastName

UPDATE:

This commit: https://github.com/mongodb/mongo-tools/commit/586c00ef09c32c77907bd20d722049ed23065398 fixes the docs for 3.0.0-rc10 and later. It changes

Fields string `long:"fields" short:"f" description:"comma separated list of field names, e.g. -f name,age"`

Fields string `long:"fields" short:"f" description:"comma separated list of field names (required for exporting CSV) e.g. -f \"name,age\" "`

VERSION 3.0 AND ABOVE:

You should use ---type=csv instead of --csv since it has been deprecated.

More details: https://docs.mongodb.com/manual/reference/program/mongoexport/#export-in-csv-format

Full command:

mongoexport --host localhost --db dbname --collection name --type=csv --out text.csv --fields firstName,middleName,lastName

回答2:

Also, you are not allowed spaces between comma separated field names.

BAD: -f firstname, lastname

GOOD: -f firstname,lastname

回答3:

mongoexport  --help
....
-f [ --fields ] arg     comma separated list of field names e.g. -f name,age
--fieldFile arg         file with fields names - 1 per line

You have to manually specify it and if you think about it, it makes perfect sense. MongoDB is schemaless; CSV, on the other hand, has a fixed layout for columns. Without knowing what fields are used in different documents it's impossible to output the CSV dump.

If you have a fixed schema perhaps you could retrieve one document, harvest the field names from it with a script and pass it to mongoexport.

回答4:

If you want, you can export all collections to csv without specifying --fields (will export all fields).

From http://drzon.net/export-mongodb-collections-to-csv-without-specifying-fields/ run this bash script

OIFS=$IFS;
IFS=",";

# fill in your details here
dbname=DBNAME
user=USERNAME
pass=PASSWORD
host=HOSTNAME:PORT

# first get all collections in the database
collections=`mongo "$host/$dbname" -u $user -p $pass --eval "rs.slaveOk();db.getCollectionNames();"`;
collections=`mongo $dbname --eval "rs.slaveOk();db.getCollectionNames();"`;
collectionArray=($collections);

# for each collection
for ((i=0; i<${#collectionArray[@]}; ++i));
do
    echo 'exporting collection' ${collectionArray[$i]}
    # get comma separated list of keys. do this by peeking into the first document in the collection and get his set of keys
    keys=`mongo "$host/$dbname" -u $user -p $pass --eval "rs.slaveOk();var keys = []; for(var key in db.${collectionArray[$i]}.find().sort({_id: -1}).limit(1)[0]) { keys.push(key); }; keys;" --quiet`;
    # now use mongoexport with the set of keys to export the collection to csv
    mongoexport --host $host -u $user -p $pass -d $dbname -c ${collectionArray[$i]} --fields "$keys" --csv --out $dbname.${collectionArray[$i]}.csv;
done

IFS=$OIFS;

回答5:

I could not get mongoexport to do this for me. I found that,to get an exhaustive list of all the fields, you need to loop through the entire collection once. Use this to generate the headers. Then loop through the collection again to populate these headers for each document.

I've written a script to do just this. Converting MongoDB docs to csv irrespective of schema differences between individual documents.

https://github.com/surya-shodan/mongoexportcsv

回答6:

Also if you want to export inner json fields use dot (. operator).

JSON record:

{
    "_id" : "00118685076F2C77",
    "value" : {
        "userIds" : [ 
            "u1"
        ],
        "deviceId" : "dev"
}

mongoexport command with dot operator (using mongo version 3.4.7):

./mongoexport --host localhost --db myDB --collection myColl --type=csv --out out.csv --fields value.deviceId,value.userIds

Output csv:

value.deviceId,value.userIds
d1,"[""u1""]"
d2,"[""u2""]"

Note: Make sure you do not export an array. It would corrupt the CSV format like field userIds shown above

回答7:

Below command used to export collection to CSV format.

Note: naag is database, employee1_json is a collection.

mongoexport --db naag--collection employee1_json --type csv --out /home/orienit/work/mongodb/employee1_csv_op1

来源：https://stackoverflow.com/questions/6814151/how-to-export-collection-to-csv-in-mongodb

标签

mongodb

csv

schemaless

database