1.导出命令
mongoDB中的mongoexport工具可以把一个collection导出成JSON格式或CSV格式的文件。可以通过参数指定导出的数据项，也可以根据指定的条件导出数据。
2.命令说明
语法：
mongoexport -d dbname -c collectionname -o file --type json/csv -f field
参数列表：
Options:
--help produce help message
-v [ --verbose ] be more verbose (include multiple times
for more verbosity e.g. -vvvvv)
--quiet silence all non error diagnostic
messages
--version print the program's version and exit
-h [ --host ] arg mongo host to connect to ( <set
name>/s1,s2 for sets)
--port arg server port. Can also use --host
hostname:port
--ipv6 enable IPv6 support (disabled by
default)
-u [ --username ] arg username
-p [ --password ] arg password
--authenticationDatabase arg user source (defaults to dbname)
--authenticationMechanism arg (=MONGODB-CR)
authentication mechanism
--gssapiServiceName arg (=mongodb) Service name to use when authenticating
using GSSAPI/Kerberos
--gssapiHostName arg Remote host name to use for purpose of
GSSAPI/Kerberos authentication
--dbpath arg directly access mongod database files
in the given path, instead of
connecting to a mongod server - needs
to lock the data directory, so cannot
be used if a mongod is currently
accessing the same path
--directoryperdb each db is in a separate directory
(relevant only if dbpath specified)
--journal enable journaling (relevant only if
dbpath specified)
-d [ --db ] arg database to use
-c [ --collection ] arg collection to use (some commands)
-f [ --fields ] arg comma separated list of field names
e.g. -f name,age
--fieldFile arg file with field names - 1 per line
-q [ --query ] arg query filter, as a JSON string, e.g.,
'{x:{$gt:1}}'
--csv export to csv instead of json
-o [ --out ] arg output file; if not specified, stdout
is used
--jsonArray output to a json array rather than one
object per line
-k [ --slaveOk ] arg (=1) use secondaries for export if
available, default true
--forceTableScan force a table scan (do not use
$snapshot)
--skip arg (=0) documents to skip, default 0
--limit arg (=0) limit the numbers of documents
returned, default all
--sort arg sort order, as a JSON string, e.g.,
'{x:1}'
说明：
-h：数据库宿主机的IP
-u：数据库用户名
-p：数据库密码
-d：数据库名字
-c：集合的名字
-f：导出的列名
-q：导出数据的过滤条件
--csv：导出格式为csv
3.示例
1）导出前10条记录：
2）导出符合查询条件的记录：
