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法律研究在使用 MongoDB 的列表查询中获得至少一项匹配值？
使用 $in 运算符进行至少一项匹配。我们先创建一个包含文档的集合 −
> db.atleastOneMatchDemo.insertOne({"StudentFavouriteSubject":["MySQL","MongoDB"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd2db5db64f4b851c3a13ce")
}
> db.atleastOneMatchDemo.insertOne({"StudentFavouriteSubject":["Java","C","MongoDB"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd2db71b64f4b851c3a13cf")
}
> db.atleastOneMatchDemo.insertOne({"StudentFavouriteSubject":["Python","C++","SQL Server"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd2db87b64f4b851c3a13d0")
}
>db.atleastOneMatchDemo.insertOne({"StudentFavouriteSubject":["Ruby","Javascript","C#","MySQL"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd2dba9b64f4b851c3a13d1")
}以下是使用 find() 方法显示集合中所有文档的查询 −
> db.atleastOneMatchDemo.find().pretty();
将生成以下输出 −
{
"_id" : ObjectId("5cd2db5db64f4b851c3a13ce"),
"StudentFavouriteSubject" : [
"MySQL",
"MongoDB"
]
}
{
"_id" : ObjectId("5cd2db71b64f4b851c3a13cf"),
"StudentFavouriteSubject" : [
"Java",
"C",
"MongoDB"
]
}
{
"_id" : ObjectId("5cd2db87b64f4b851c3a13d0"),
"StudentFavouriteSubject" : [
"Python",
"C++",
"SQL Server"
]
}
{
"_id" : ObjectId("5cd2dba9b64f4b851c3a13d1"),
"StudentFavouriteSubject" : [
"Ruby",
"Javascript",
"C#",
"MySQL"
]
}以下是进行至少一项匹配的查询 −
>db.atleastOneMatchDemo.find({"StudentFavouriteSubject":{"$in":["MongoDB","MySQL"]}}).pretty();将生成以下输出 −
{
"_id" : ObjectId("5cd2db5db64f4b851c3a13ce"),
"StudentFavouriteSubject" : [
"MySQL",
"MongoDB"
]
}
{
"_id" : ObjectId("5cd2db71b64f4b851c3a13cf"),
"StudentFavouriteSubject" : [
"Java",
"C",
"MongoDB"
]
}
{
"_id" : ObjectId("5cd2dba9b64f4b851c3a13d1"),
"StudentFavouriteSubject" : [
"Ruby",
"Javascript",
"C#",
"MySQL"
]
}
更新于： 2019 年 7 月 30 日
387 次浏览
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