MongoDB for Developers with Python Transcripts
Chapter: Course conclusion
Lecture: Lightning review: Shell query syntax
0:01 The MongoDB shell and native query syntax;
0:03 we saw that the MongoDB shell which you start by typing the word 'mongo'
0:07 and it just runs the shell, tries to talk to the local one,
0:10 there's all the different ways to get it to connect to different servers as we've seen.
0:13 So once it starts you get this little greater than prompt
0:24 and actually this is converted to bson a binary extended version of json.
0:29 So here we type something like db so this is the database we have active
0:33 and book would be the collection name
0:35 or table if you're still thinking relationally, but the collection name,
0:38 and we say things like find or count or sort, or things like this
0:42 and what we give it is this prototypical json object
0:45 and what we get back are all the things that match the elements of that prototype.
0:50 So here you can see we got two records back
0:53 and they both had the same title as the title we indicated here.
0:56 So it's very much about passing these prototypical json documents,
1:00 however sometimes we have to do more than just say
1:04 I want basically equality in my search,
1:07 I would like to express things like greater than.
1:09 So this query here that we have written
1:12 is actually doing a couple of very interesting things,
1:14 maybe the thing that stands out the most is this greater than operator,
1:17 so the dollar gte is indicating, the dollar indicates an operator,
1:20 and gte is the name the greater than or equal to operator,
1:23 so instead of just saying ratings.value is nine,
1:26 we're saying I'd like all the ratings where the value is either equal to or greater than nine.
1:30 The other powerful and interesting thing here is
1:33 we're actually traversing this hierarchy of the document
1:36 we're going to find the ratings array which is a list of subdocuments
1:39 which has a value as an integer,
1:41 so we're actually reaching down inside that document
1:44 and we're doing this query with this operator.