MongoDB中的SQL“ like”等效项是什么？
您可以使用“$regex”运算符在MongoDB中实现与SQL“like”等效的功能。为了实现它，让我们创建一个带有文档的集合。使用文档创建集合的查询如下-
> db.sqlLikeDemo.insertOne({"UserName":"John Smith","UserAge":24});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c912e124afe5c1d2279d6a5")
}
> db.sqlLikeDemo.insertOne({"UserName":"John Doe","UserAge":21});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c912e264afe5c1d2279d6a6")
}
> db.sqlLikeDemo.insertOne({"UserName":"Chris Williams","UserAge":22});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c912e404afe5c1d2279d6a7")
}
> db.sqlLikeDemo.insertOne({"UserName":"Robert Taylor","UserAge":26});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c912e4d4afe5c1d2279d6a8")
}
> db.sqlLikeDemo.insertOne({"UserName":"John Brown","UserAge":27});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c912e6c4afe5c1d2279d6a9")
}
> db.sqlLikeDemo.insertOne({"UserName":"Mike Brown","UserAge":23});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c912e794afe5c1d2279d6aa")
}
> db.sqlLikeDemo.insertOne({"UserName":"Larry Smith","UserAge":24});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c912e8c4afe5c1d2279d6ab")
}在find()method的帮助下显示集合中的所有文档。查询如下-
> db.sqlLikeDemo.find().pretty();
以下是输出-
{
"_id" : ObjectId("5c912e124afe5c1d2279d6a5"),
"UserName" : "John Smith",
"UserAge" : 24
}
{
"_id" : ObjectId("5c912e264afe5c1d2279d6a6"),
"UserName" : "John Doe",
"UserAge" : 21
}
{
"_id" : ObjectId("5c912e404afe5c1d2279d6a7"),
"UserName" : "Chris Williams",
"UserAge" : 22
}
{
"_id" : ObjectId("5c912e4d4afe5c1d2279d6a8"),
"UserName" : "Robert Taylor",
"UserAge" : 26
}
{
"_id" : ObjectId("5c912e6c4afe5c1d2279d6a9"),
"UserName" : "John Brown",
"UserAge" : 27
}
{
"_id" : ObjectId("5c912e794afe5c1d2279d6aa"),
"UserName" : "Mike Brown",
"UserAge" : 23
}
{
"_id" : ObjectId("5c912e8c4afe5c1d2279d6ab"),
"UserName" : "Larry Smith",
"UserAge" : 24
}这是类似于SQL'like'子句的查询，即带有“UserName”John的记录-
> db.sqlLikeDemo.find({"UserName":{"$regex": "John"}}).pretty();以下是输出-
{
"_id" : ObjectId("5c912e124afe5c1d2279d6a5"),
"UserName" : "John Smith",
"UserAge" : 24
}
{
"_id" : ObjectId("5c912e264afe5c1d2279d6a6"),
"UserName" : "John Doe",
"UserAge" : 21
}
{
"_id" : ObjectId("5c912e6c4afe5c1d2279d6a9"),
"UserName" : "John Brown",
"UserAge" : 27
}