one. Conditional operator:
(>) greater than - $gt
(<) less than - $lt
(>=) greater than or equal to - $gte
(<= ) less than or equal to - $lte
example:
>use date
switched to db date
>db.users.insert([{'name':'Ada','age':20},{'name':'Aer','age':25},{'name':'Asan ','age':30}])
>db.users.find({"age" : {$gt : 22}})
[{'name':'Aer','age':25},{'name':'Asan','age':30}]
This is a query about the greater than operator. The rest of the operators are similar.
two. $all matches all values.
example:
>db.users.insert([{'name':'阿大','age':20,'kk':[10,20,30]},
{'name':'A'er','age':25,'kk':[10,22,30]},
{'name':'Asan','age':30,'kk':[10,22,32]
}])
>db.users.find({"kk" : {$all:[10,22]}})
[{'name':'A'er','age':25,'kk':[10,22,30]},
{'name':'Asan','age':30,'kk':[10,22,32]}
]
The value in the query key kk contains all the information of [10.22].
3. The value contained in the $in query
example:
>db.users.insert([{'name':'阿大','age':20,'kk':[10,20,30]},
{'name':'A'er','age':25,'kk':[10,22,30]},
{'name':'Asan','age':30,'kk':[10,22,32]
}])
>db.users.find({"age" : {$in:[24,31]}})
[{'name':'A'er','age':25,'kk':[10,22,30]},
{'name':'Asan','age':30,'kk':[10,22,32]}
]
The value of the query key age 24=<age<=31.
Four. $exists determines whether the field exists (true exists, false does not exist)
example:
>db.users.find({'age':{$exists:false)