_4_ operator MongoDB study notes

Operators

Comparison operators

No.	symbol	meaning
1	$eq	equal
2	$lt	Less than
3	$ lte	Less than or equal
4	$gt	more than the
5	$gte	greater or equal to
6	$ does	not equal to
7	$in	contain
8	$ s	Does not contain

• eg db.class.find({age:{$eq:22}},{_id:0，name:1})
• eg db.class.find({age:{$lt:22}},{_id:0，name:1})
• eg db.class.find({age:{$in:[22,23]]}},{_id:0，name:1})

Logical Operators

No.	symbol	meaning
1	$and	Logic and
2	$or	Logical or
3	$not	Logical NOT
4	$nor	Neither nor

• eg db.class.find({$or:[{age:{$lt:22}},{sex:'w'}]},{_id:0，name:1})

Find Array

No.	symbol	meaning
1	$all	Find the array contains a number of documents
2	$size	Find the number of items in the array to the specified number of documents
3	$slice	Several display array ago

• eg display first hobby db.class.find({},{hobby:{$slice:1}})
• After skipping the first two eg, display hobby db.class.find({},{hobby:{$slice:[1,2]}})

other

No.	symbol	meaning
1	$exist	Determining whether there is a field
2	$mod	Remainder
3	$type	Find the value of specified types of documents

• eg find documents exist sex domain db.class.find({sex:{$exists:true},{_id:0}})
• eg Find age divisible by 3 documents db.class.find({age:{$mod:[3,0]},{_id:0}})

Query commonly used functions

No.	symbol	meaning
1	distinct())	The value of a field of view covered by the scope of the collection
2	pretty()	Formatted output
3	limit(n)	Query results are displayed first n documents
4	skip(n)	Skip the first n lines of the document display
5	count()	count
6	sort()	Sort by the specified field
5	count()	count