mongoDB如何query is Null

试了半天，原来通过

db.taobaoItem.find({"coupon_price":{$ne:null}}

MongoDB Operators

Query Selectors

Comparison

Name Description

$all	Matches arrays that contain all elements specified in the query.
$gt	Matches values that are greater than the value specified in the query.
$gte	Matches values that are equal to or greater than the value specified in the query.
$in	Matches any of the values that exist in an array specified in the query.
$lt	Matches values that are less than the value specified in the query.
$lte	Matches values that are less than or equal to the value specified in the query.
$ne	Matches all values that are not equal to the value specified in the query.
$nin	Matches values that do not exist in an array specified to the query.

Logical

Name Description

$or	Joins query clauses with a logical OR returns all documents that match the conditions of either clause.
$and	Joins query clauses with a logical AND returns all documents that match the conditions of both clauses.
$not	Inverts the effect of a query expression and returns documents that do not match the query expression.
$nor	Joins query clauses with a logical NOR returns all documents that fail to match both clauses.

Element

Name Description

$exists	Matches documents that have the specified field.
$mod	Performs a modulo operation on the value of a field and selects documents with a specified result.
$type	Selects documents if a field is of the specified type.

JavaScript

Name Description

$where	Matches documents that satisfy a JavaScript expression.
$regex	Selects documents where values match a specified regular expression.

Geospatial

Name Description

$geoWithin	Selects geometries within a bounding GeoJSON geometry.
$geoIntersects	Selects geometries that intersect with a GeoJSON geometry.
$near	Returns geospatial objects in proximity to a point.
$nearSphere	Returns geospatial objects in proximity to a point on a sphere.

Array

Name Description

$elemMatch	Selects documents if element in the array field matches all the specified $elemMatch condition.
$size	Selects documents if the array field is a specified size.

Update Operators

Fields

Name Description

$inc	Increments the value of the field by the specified amount.
$rename	Renames a field.
$setOnInsert	Sets the value of a field upon documentation creation during an upsert. Has no effect on update operations that modify existing documents.
$set	Sets the value of a field in an existing document.
$unset	Removes the specified field from an existing document.

Array

Operators

Name Description

$	Acts as a placeholder to update the first element that matches the query condition in an update.
$addToSet	Adds elements to an existing array only if they do not already exist in the set.
$pop	Removes the first or last item of an array.
$pullAll	Removes multiple values from an array.
$pull	Removes items from an array that match a query statement.
$pushAll	Deprecated. Adds several items to an array.
$push	Adds an item to an array.

Modifiers

Name Description

$each	Modifies the $push and $addToSet operators to append multiple items for array updates.
$slice	Modifies the $push operator to limit the size of updated arrays.
$sort	Modifies the $push operator to reorder documents stored in an array.

Bitwise

Name Description

$bit	Performs bitwise AND and OR updates of integer values.

Isolation

Name Description

$isolated	Modifies behavior of multi-updates to improve the isolation of the operation.

Projection Operators

Name Description

$	Projects the first element in an array that matches the query condition.
$elemMatch	Projects only the first element from an array that matches the specified $elemMatch condition.
$slice	Limits the number of elements projected from an array. Supports skip and limit slices.

Meta-Query Operators

Query Modifiers

Name Description

$comment	Adds a comment to the query to identify queries in the database profiler output.
$explain	Forces MongoDB to report on query execution plans. See explain().
$hint	Forces MongoDB to use a specific index. See hint()
$maxScan	Limits the number of documents a cursor will return for a query. See limit().
$max	Specifies a minimum exclusive upper limit for the index to use in a query. See max().
$min	Specifies a minimum inclusive lower limit for the index to use in a query. See min().
$orderby	Returns a cursor with documents sorted according to a sort specification. See sort().
$returnKey	Forces the cursor to only return fields included in the index.
$showDiskLoc	Modifies the documents returned to include references to the on-disk location of each document.
$snapshot	Forces the query to use the index on the _id field. See snapshot().

Sort Order Specifier

Name Description

$natural	A special sort order that orders documents using the order of documents on disk.