This is going to be a short post for all the people out there who’re new to MongoDB. I had to dive into MongoDB as part of a new project that I joined. I was asked to write a Map-Reduce job, and in the process decided to run a few queries on MongoDB.
I found out that there was a $lte and a $gte operator. But no $eq operator. It baffled me that there was no way to check for equality. I searched a bit but found no option, so I used an $and operator and did a $lte AND $gte, effectively getting a $eq operator.
But now I know better. To check for equality in MongoDB, you just put the second value as the second parameter.
db.test.find({"a":123})
This checks if the field named a equals 123.
That’s about it. Simple, but not quite straightforward to a person fresh out of the RDBMs world and new to MongoDB :)