"MongoDB First Knowledge"-conditional operator

1, the condition >,<,>=,<= in MongoDB the wording

: $gt, <: $lt, >=: $gte, <=: $lte, <>: $ne

Specific Use method:

Db.class.find ({"filed": {$GT: Value}}) Filed>value

Db.class.find ({"filed": {$lt: Value}}) Filed<value

Db.class.find ({"filed": {$gte: Value}}) Filed>=value

Db.class.find ({"filed": {$lte: Value}}) Filed<=value

Db.class.find ({"filed": {$gt: Value, $lt: value1}}) Value1>filed>value

Db.class.find ({"filed": {$ne: 5}}) Filed<>value

Db.class.find ({"Stucount": {$gt:ten}}) Db.class.find ({"Stucount": {$gte:Ten}})

Db.class.find ({"Stucount": {$lt:ten}}) Db.class.find ({"Stucount": {$lte:Ten}})

Db.class.find ({"Stucount": {$lt:ten, $gt:5}})
Db.class.find ({"Stucount": {$ne: 5}})

2. $all Match All

This operator is similar to the SQL syntax in, but the difference is that in only one value of () is satisfied, and the $all must be
All values within [] must be met

Db.class.find ({stucount:{$all: [6,8]}}) query result is empty

Db.class.find ({stucount:{$all: [6]}) can find one, equivalent to Db.class.find ({"Stucount": 6})

3. $in contains

Is the same as the purpose of SQL standard syntax, which is to query a range of enumerated values

Db.class.find ({stucount:{$in: [6,8]}})

4. $nin does not contain

Db.class.find ({stucount:{$nin: [6,8]}})

5. Determine if a field exists

Db.class.find ({stucount:{$exists: true}})

6. Null value processing

Db.class.find ({name:null}) will query for data that does not have a name field

Db.class.find ({name:{"$in": [null], "$exists": True}}) The query result has a name field and Name=null

7, $mod to take surplus

Db.class.find ({stucount:{$mod: [7,2]}}) equals 2 for 7

"MongoDB First Knowledge"-conditional operator