MongoDB (Lesson 7 logic operations)

3.4.2.2 Logical operation

There are three main types of logical operations: with ($and), or ($or), non ($not, $nor).

Example: Querying student information for age in 20~21岁

Db.students.find ({"Age": {"$gte": +, "$lte": +}}). Pretty ()

The "and" connection is easiest when it comes to logic, because you only need to use the "," to separate the conditions.

Example: query information for students older than 19 years or more than 90 score

Db.students.find ({"$or": [{"$gt": {"}}}, {" score ": {" $GT ": +}]}). Pretty ()

Or the connection needs to set the filter for the data array, that is, add the brackets.

Example: to do or reverse an action

Db.students.find ({"$nor": [{"$gt": {"}}}, {" score ": {" $GT ": +}]}). Pretty ()

MongoDB (Lesson 7 logic operations)