Query Operators

• Query operators provide additional ways to locate data within a database
  • The $ in mongoDB is used for various different purposes
    • precedes MQL Operators
    • precedes Aggregation pipeline stages
    • allow access to field values

Comparison Operators

• $eq - Equal To operator
• $ne - Not Equal To operator
• $gt / $gte - Greater than or Greater than equal to
• $lt / $lte - Less than or Less than Equal to

same syntax as before, i.e. -

{ <field> : { <operator> : <value> } }

For example, let's say from the sample_training.trips dataset, we need to find all the users that travelled for less than or equal to 70 seconds and not a subscriber. The query for the same would be

db.trips.find({"trip duration" : {"$lte": 70} }, "usertype": { "$ne": "subscriber"})

Logic Operators

• A set of four logical operators
  • $and
  • $or
  • $nor
  • $not
• Except $not all the other operators has the same syntax

db.collection_name.find(<operator>: [{condition1}, {condition2}...]

• Syntax for $not

db.collection_name.find("$not": {condition})

For example, let's say we want all the documents in the inspections collection that does not have the result category of Pass, Fail, Violation Issued and No Violation Issued