|
"_id" : ObjectId("4ffcb2ed65282ea95f7e3304"),
"age" : 23,
"favorite" : {
"1" : "reading",
"2" : "swimming",
"3" : "listening music"
},
"fname" : "jeff",
"height" : 166,
"lname" : "jiang",
"relationships" : [
{
"age" : 22,
"fname" : "qiang",
"lname" : "he"
},
{
"fname" : "deng",
"lname" : "pan"
},
{
"fname" : "xiong",
"lname" : "lan"
}
]
}
可是很多情况下，不预先查询文档我们就不知道要修改数组的元素的下标。这时定位操作符“$”就很好用了。它就是用来定位查询文档已匹配的元素，并进行更新。我们来看看它怎么用：
> db.user.update({"relationships.fname":"xiong"},{$set:{"relationships.$.age":22}})
> db.user.findOne()
{
"_id" : ObjectId("4ffcb2ed65282ea95f7e3304"),
"age" : 23,
"favorite" : {
"1" : "reading",
"2" : "swimming",
"3" : "listening music"
},
"fname" : "jeff",
"height" : 166,
"lname" : "jiang",
"relationships" : [
{
"age" : 22,
"fname" : "qiang",
"lname" : "he"
},
{
"age" : 22,
"fname" : "deng",
"lname" : "pan"
},
{
"age" : 22,
"fname" : "xiong",
"lname" : "lan"
}
]
}
|