数据转移有多种方案，本质上需要将mysql数据转换为一种MongoDB可以直接导入的格式即可。MongoDB提供了mongoimport工具，可以支持导入json,csv的格式。
先来看一下mongoimport支持的参数：
$ mongoimport --help
options:
--help produce help message
-v [ --verbose ] be more verbose (include multiple times for more
verbosity e.g. -vvvvv)
-h [ --host ] arg mongo host to connect to ( /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
--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 if dbpath specified, each db is in a separate
directory
-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 fields names - 1 per line
--ignoreBlanks if given, empty fields in csv and tsv will be ignored
--type arg type of file to import. default: json (json,csv,tsv)
--file arg file to import from; if not specified stdin is used
--drop drop collection first
--headerline CSV,TSV only - use first line as headers
--upsert insert or update objects that already exist
--upsertFields arg comma-separated fields for the query part of the
upsert. You should make sure this is indexed
--stopOnError stop importing at first error rather than continuing
--jsonArray load a json array, not one item per line. Currently
limited to 4MB.
由上面的帮助文档可以看出，采用csv作为中间数据格式，无论对于mysql的导出，还是mongodb的导入，都算得上是成本最低了，于是一回就尝试了一把：
首先，将mysql数据库中的wp-posts表导出，一回偷懒了，直接用phpmyadmin的导出功能，选择csv格式导出，并选中了“删除字段中的换行符”以及“将字段名放在第一行”，保存文件名为csser.csv。
接着，到mongodb服务器，shell下连接MongoDB数据库，并进行数据导入：
$ mongoimport -d csser -c posts -type csv -file csser.csv --headerline
connected to: 127.0.0.1
imported 548 objects
$ mongo
MongoDB shell version: 1.8.1
connecting to: test
> use csser
switched to db csser
> db.posts.count()
547
> db.posts.find({}, {"post_title":1}).sort({"ID":-1}).limit(1)
{ "_id" : ObjectId("4df4641d31b0642fe609426d"), "post_title" : "CSS Sprites在线应用推荐-CSS-sprit" }