$不执行和操作

Question

I just started exploring mongoDB. During that time I managed to create a simple collection with the following data,

db.test.insert({name : "joe", age : 20});
db.test.insert({name: "james", age : 25});

Now I have queried it by using,

db.test.find({name : {$not : {$eq : "joe", $eq: "james"}}})

It yielded me the following result,

{name : "joe", age : 20}

I am confused here, Is it not an and operation like below,

SELECT * FROM test where not name = "joe" and not name = "james"

Doubt1: If yes then how the above mentioned mongo query can be interpreted as a normal mysql query? [Note : I am coming from a mysql background.] Please explain.

Doubt2: Also explain about the following mongo query,

db.test.find({name : "joe", age : 20});

Is the above query equals to select * from test where name='joe' and age=20 ? If not then how it would be interpreted as a normal mysql query?

Answer 1

When you are creating an object with {$eq : "joe", $eq: "james"} you are using the same object key twice. So james will overwrite joe because both use the same object key $eq .

To do your query, you can try something like NOT (name = "joe" OR name = "james") . So you add the OR to your mongo query:

db.test.find({name : {$nor: [{$eq: "joe"}, $eq: "james"]}})

Reference

Answer 2

I guess Christoph cleared your doubts.

For SQL to Mongo Query reference visit this link