如何将 mongodb 类型从 Double 或 Integer 更改为 String？
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How to change a mongodb type from Double or Integer to String?
提问by Alex Ryan
I used mongoimport to import some csv data into mongodb.
我使用 mongoimport 将一些 csv 数据导入到 mongodb 中。
It mostly created types correctly but there are a few instances where Doubles or Integers were created where Strings are desired.
它主要正确创建了类型，但也有一些实例在需要字符串的地方创建了双精度型或整数型。
I've tried several techniques to convert these fields to strings to no avail.
我尝试了多种技术将这些字段转换为字符串，但无济于事。
Here's what I have tried:
这是我尝试过的：
This produced an undesired change to an Object type (type=3):
这对对象类型（type=3）产生了不希望的变化：
db.temp.find( { 'name' : { $type : 16 } } ).forEach( function (x) {
x.name = new String(x.name); // convert field to string
db.temp.save(x);
});
Result looked like this:
结果如下所示：
> db.temp.findOne({name: {$type:3}})
{
"_id" : ObjectId("541a28ddbf8a2e3ee8439b58"),
"name" : {
"0" : "0",
"1" : ".",
"2" : "2",
"3" : "2"
}
}
This produced no change:
这没有产生任何变化：
db.temp.find({name: {$exists:true}}).forEach( function(x) {
x.name = "" + x.name;
});
This produced no change:
这没有产生任何变化：
db.temp.find({name: {$exists:true}}).forEach( function(x) {
x.name = x.name + "";
});
This produced no change:
这没有产生任何变化：
db.temp.find({name: {$exists:true}}).forEach( function(x) {
x.name = "" + x.name + "";
});
This produced no change:
这没有产生任何变化：
db.temp.find({name: {$exists:true}}).forEach( function(x) {
x.name = x.name.toString();
});
This produced an error: TypeError: Object 0.22 has no method 'toNumber'
这产生了一个错误：TypeError: Object 0.22 has no method 'toNumber'
db.temp.find({name: {$exists:true}}).forEach( function(x) {
x.name = x.name.toNumber().toString();
});
回答by yaoxing
If you want to store the converted data, you'll need to updatethe document, otherwise the changed document goes to no where.
如果要存储转换后的数据，则需要update文档，否则更改的文档无处可去。
db.temp.find({name: {$exists:true}}).forEach( function(x) {
db.temp.update({_id: x._id}, {$set: {name: x.name.toString()}});
});
As to the toNumberissue, it's not an build-in function. You may want to use parseIntor parseFloatinstead:
至于这个toNumber问题，它不是一个内置函数。您可能想要使用parseInt或parseFloat代替：
parseInt("1000"); // output: 1000
回答by Jaymin
Convert Int to str:
将 Int 转换为 str：
db.dbname.find({fieldname: {$exists: true}}).forEach(function(obj) {
obj.fieldname= "" + obj.fieldname;
db.dbname.save(obj); });
I tried using this query. It was working for me. I think it is support till mongodb 3.4. In latest one might be now work.
我尝试使用此查询。它对我有用。我认为它是支持直到 mongodb 3.4。在最新的一个可能现在工作。
