向 集合 添加新文档
从 集合 里删除文档
更新 现有文档
1. 插入并保存文档
> db.foo.insert({ " bar ": " baz "})
这个操作会给文档增加一个"_id"键 （如果 原来没有这个键的话），然后保存到MongoDB中
> db.foo.find() { " _id " : ObjectId( " 4fdc779a89834bfb0bd267a3 "), " bar " : " baz " }
文档不能超过 4 MB ， 可以 用 Object.bsonsize( 文档 ) 查看文档转换为 BSON 的大小 （以 字节 为 单位）
> post = { " title ": " My Blog post ", " content ": " Here's my blog post. ", " date ": ... new Date()} { " title " : " My Blog post ", " content " : " Here's my blog post. ", " date " : ISODate( " 2012-06-16T12:19:25.163Z ") } > Object.bsonsize(post) 77
2. 删除文档
db.foo.remove() 会删除foo集合中所有的文档，当不会删除集合本身，原来的索引也会保留。
> db.foo.findOne() { " _id " : ObjectId( " 4fdc779a89834bfb0bd267a3 "), " bar " : " baz " } > show collections foo system.indexes > db.foo.remove() > show collections foo system.indexes > db.foo.find() >
remove() 函数可以接受 一个查询文档 作为可选 参数， 这样只有符合条件的参数 才被删除。
> post2 = { " title ": " My Blog post2 ", " content ": " Here's my blog post2. ", " date ": ... new Date()} { " title " : " My Blog post2 ", " content " : " Here's my blog post2. ", " date " : ISODate( " 2012-06-16T12:41:34.429Z ") } > db.foo.insert(post2) > db.foo.find() { " _id " : ObjectId( " 4fdc7e1889834bfb0bd267a4 "), " title " : " My Blog post ", " content " : " Here's my blog post. ", " date " : ISODate( " 2012-06-16T12:19:25.163Z ") } { " _id " : ObjectId( " 4fdc7f2689834bfb0bd267a5 "), " title " : " My Blog post2 ", " content " : " Here's my blog post2. ", " date " : ISODate( " 2012-06-16T12:41:34.429Z ") } > db.foo.remove({ " title " : " My Blog post2 "}) > db.foo.find() { " _id " : ObjectId( " 4fdc7e1889834bfb0bd267a4 "), " title " : " My Blog post ", " content " : " Here's my blog post. ", " date " : ISODate( " 2012-06-16T12:19:25.163Z ") } >
remove 删除数据是永久性的，不能撤销，也不能恢复。
另一个 删除命令 db.runCommand({
"drop":"foo"}) 。3. 更新
最简单的方法 用一个新文档 替换 原文档。 这种 适用于 结构变化较大的时候。
> user = { " name " : " joe ", ... " friends ":32, ... " enemies ":2 ... } { " name " : " joe ", " friends " : 32, " enemies " : 2 } > db.user.insert(user) > db.user.find() { " _id " : ObjectId( " 4fdc893d89834bfb0bd267a6 "), " name " : " joe ", " friends " : 32, " enemies " : 2 }
例如：
{
"_id" : ObjectId("4fdc893d89834bfb0bd267a6"),
"name" : "joe" ,
"friends" : 32 ,
"enemies" : 2
}
改变为
{
"_id" : ObjectId("4fdc893d89834bfb0bd267a6"),
"username" : "joe" ,
"relationships" :
{
"friends" : 32 ,
"enemies" : 2
}
}
可以用update 来替换文档：
> var joe = db.user.findOne({ " name ": " joe "}) > joe.relationships = { " friends ":joe.friends , " enemies " : joe.enemies}; { " friends " : 32, " enemies " : 2 } > joe.username = joe.name joe > delete joe.name true > delete joe.friends true > delete joe.enemies true > db.user.find() { " _id " : ObjectId( " 4fdc893d89834bfb0bd267a6 "), " name " : " joe ", " friends " : 32, " enemies " : 2 } > db.user.update({ " name " : " joe " },joe); > db.user.find() { " _id " : ObjectId( " 4fdc893d89834bfb0bd267a6 "), " relationships " : { " friends " : 32, " enemies " : 2 }, " username " : " joe " } >