MongoDB and Python

MongoDB Query Operators

As mentioned previously, MongoDB has quite a rich set of query operators and predicates. In Table 2-2 we provide a table with the meaning of each one, along with a sample usage and the SQL equivalent where applicable.

Table 2-2. MongoDB query operators

Operator	Meaning	Example	SQL Equivalent
$gt	Greater Than	“score”:{"$gt”:0}	>
$lt	Less Than	“score”:{"$lt”:0}	<
$gte	Greater Than or Equal	“score”:{"$gte”:0}	>=
$lte	Less Than or Equal	“score”:{"$lte”:0}	⇐
$all	Array Must Contain All	“skills”:{"$all”:["mongodb”,"python"]}	N/A
$exists	Property Must Exist	“email”:{"$exists”:True}	N/A
$mod	Modulo X Equals Y	“seconds”:{"$mod”:[60,0]}	MOD()
$ne	Not Equals	“seconds”:{"$ne”:60}	!=
$in	In	“skills”:{"$in”:["c”,"c++"]}	IN
$nin	Not In	“skills”:{"$nin”:["php”,"ruby”,"perl"]}	NOT IN
$nor	Nor	“$nor”:[{"language”:"english"},{"country”:"usa"}]	N/A
$or	Or	“$or”:[{"language”:"english"},{"country”:"usa"}]	OR
$size	Array Must Be Of Size	“skills”:{"$size”:3}	N/A

If you do not fully understand the meaning or purpose of some of these operators immediately do not worry. We shall discuss the practical use of some of the more advanced operators in detail in Chapter 3.