MongoDB查询以从文档中删除数组元素？
使用$pull从MongoDB文档中删除数组元素，如以下语法所示-
db.yourCollectionName.update( { },{ $pull: { yourFieldName: yourValue }},{multi:true });首先让我们创建一个包含文档的集合-
>db.removeArrayElementsDemo.insertOne({"AllPlayerName":["John","Sam","Carol","David"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd90d011a844af18acdffc1")
}
>db.removeArrayElementsDemo.insertOne({"AllPlayerName":["Chris","Robert","John","Mike"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd90d2e1a844af18acdffc2")
}以下是在find()方法的帮助下显示集合中所有文档的查询-
> db.removeArrayElementsDemo.find().pretty();
这将产生以下输出-
{
"_id" : ObjectId("5cd90d011a844af18acdffc1"),
"AllPlayerName" : [
"John",
"Sam",
"Carol",
"David"
]
}
{
"_id" : ObjectId("5cd90d2e1a844af18acdffc2"),
"AllPlayerName" : [
"Chris",
"Robert",
"John",
"Mike"
]
}这是从文档中删除数组元素的查询-
> db.removeArrayElementsDemo.update( { },{ $pull: { AllPlayerName: "John" }},{multi:true });
WriteResult({ "nMatched" : 2, "nUpserted" : 0, "nModified" : 2 })让我们再次检查所有文件-
> db.removeArrayElementsDemo.find().pretty();
这将产生以下输出-
{
"_id" : ObjectId("5cd90d011a844af18acdffc1"),
"AllPlayerName" : [
"Sam",
"Carol",
"David"
]
}
{
"_id" : ObjectId("5cd90d2e1a844af18acdffc2"),
"AllPlayerName" : [
"Chris",
"Robert",
"Mike"
]
}