$type操作符是基于BSON类型来检索集合中匹配的数据类型，并返回结果。
| 类型 | 数字 | 备注 |
|---|---|---|
| Double | 1 | |
| String | 2 | |
| Object | 3 | |
| Array | 4 | |
| Binary data | 5 | |
| Undefined | 6 | 已废弃。 |
| Object id | 7 | |
| Boolean | 8 | |
| Date | 9 | |
| Null | 10 | |
| Regular Expression | 11 | |
| JavaScript | 13 | |
| Symbol | 14 | |
| JavaScript (with scope) | 15 | |
| 32-bit integer | 16 | |
| Timestamp | 17 | |
| 64-bit integer | 18 | |
| Min key | 255 | Query with -1. |
| Max key | 127 |
使用find()命令查看数据：
> db.col.find().pretty()
{
"_id" : ObjectId("5f18f92eb5775c49914787b3"),
"title" : "我是一个标题",
"description" : "MongoDB 是一个 Nosql 数据库",
"by" : "tre",
"url" : "http://www.tre.com",
"tags" : [
"mongodb",
"database",
"NoSQL"
],
"likes" : 90
}
{
"_id" : ObjectId("5f18f9d8b5775c49914787b4"),
"title" : "我是一个标题",
"description" : "MongoDB 是一个 Nosql 数据库",
"by" : "tre",
"url" : "http://www.tre.com",
"tags" : [
"mongodb",
"database",
"NoSQL"
],
"likes" : 100
}
{
"_id" : ObjectId("5f18f9dab5775c49914787b5"),
"title" : "我是一个标题",
"description" : "MongoDB 是一个 Nosql 数据库",
"by" : "tre",
"url" : "http://www.tre.com",
"tags" : [
"mongodb",
"database",
"NoSQL"
],
"likes" : 110
}
MongoDB 操作符 - $type 实例
db.col.find({"title" : {$type : 2}})
或
db.col.find({"title" : {$type : 'string'}})
输出结果为：
> db.col.find({"title":{$type:'string'}}).pretty()
{
"_id" : ObjectId("5f18f92eb5775c49914787b3"),
"title" : "我是一个标题",
"description" : "MongoDB 是一个 Nosql 数据库",
"by" : "tre",
"url" : "http://www.tre.com",
"tags" : [
"mongodb",
"database",
"NoSQL"
],
"likes" : 90
}
{
"_id" : ObjectId("5f18f9d8b5775c49914787b4"),
"title" : "我是一个标题",
"description" : "MongoDB 是一个 Nosql 数据库",
"by" : "tre",
"url" : "http://www.tre.com",
"tags" : [
"mongodb",
"database",
"NoSQL"
],
"likes" : 100
}
{
"_id" : ObjectId("5f18f9dab5775c49914787b5"),
"title" : "我是一个标题",
"description" : "MongoDB 是一个 Nosql 数据库",
"by" : "tre",
"url" : "http://www.tre.com",
"tags" : [
"mongodb",
"database",
"NoSQL"
],
"likes" : 110
}
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