Overview of Filter Logical Combining Operators

You use filter logical combining operators, $and, $or, and $nor, to combine conditions to form more complex filters. Each accepts an array of conditions as its argument.

Filter logical combining operator $and matches a document if each condition in its array argument matches it. For example, this filter matches Example 2-1, because that document contains a field name whose value starts with "Ja", and it contains a field drinks whose value is "tea".

{"$and" : [ {"name" : {"$startsWith" : "Ja"}}, {"drinks" : "tea"} ]}

Often you can omit operator $and — it is implicit. For example, the following query is equivalent to the previous one:

{"name" : {"$startsWith" : "Ja"}, "drinks" : "tea"}

Filter logical combining operator $or matches a document if at least one of the conditions in its array argument matches it.

For example, the following filter matches Example 2-2 and Example 2-3, because those documents contain a field drinks whose value is "soda" or they contain a field zip under a field address, where the value of address.zip is less than 94000, or they contain both:

{"$or" : [ {"drinks" : "soda"}, {"address.zip" : {"$le" : 94000}} ]}

Filter logical combining operator $nor matches a document if no condition in its array argument matches it. (Operators $nor and $or are logical complements.)

The following query matches sample document 1, because in that document there is neither a field drinks whose value is "soda" nor a field zip under a field address, where the value of address.zip is less than 94000:

{"$nor" : [ {"drinks" : "soda"}, {"address.zip" : {"$le" : 94000}} ]}

Each element in the array argument of a logical combining operator is a condition.

For example, the following condition has a single logical combining clause, with operator $and. The array value of $and has two conditions: the first condition restricts the value of field age. The second condition has a single logical combining clause with $or, and it restricts either the value of field name or the value of field drinks.

{ "$and" : [ { "age" : {"$gte" : 60} },
             { "$or" : [ {"name" :  "Jason"},
                         {"drinks" : {"$in" : ["tea", "soda"]}} ] } ] }

The condition with the comparison for field age matches sample document 3.
The condition with logical combining operator $or matches sample documents 1 and 3.
The overall condition matches only sample document 3, because that is the only document that satisfies both the condition on age and the condition that uses $or.

The following condition has two conditions in the array argument of operator $or. The first of these has a single logical combining clause with $and, and it restricts the values of fields name and drinks. The second has a single logical combining clause with $nor, and it restricts the values of fields age and name.

{ "$or" : [ { "$and" : [ {"name" : "Jason"},
                         {"drinks" : {"$in" : ["tea", "soda"]}} ] },
            { "$nor" : [ {"age" : {"$lt" : 65}},
                         {"name" : "Jason"} ] } ] }

The condition with operator $and matches sample document 1.
The condition with operator $nor matches sample document 3.
The overall condition matches both sample documents 1 and 3, because each of these documents satisfies at least one condition in the $or argument.

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