Run in the bin directory, the db directory must have been created in advance, otherwise save it, and then you can use it
mongod --dbpath d:\data\dbThe default login does not require authentication. Can use compass for more intuitive use
create database
Use use to point to the database if it does not exist, but if no data is added, the database will still not be created
As you can see, the database will only be created after the operation is performed
remove use
db.dropDatabase()
Revise
By default update only modifies the first found data, and if set is not used, the entire document will be replaced
To modify multiple lines, you need to use the set and multi keywords, which match 10 records, but only 9 records have been modified due to the previous modification
save, if _id already exists, replace the original document, if not, add and set _id
db.lost.save({
'_id': ObjectId('5a7faa972054091f9ceeeb01'),
'name': 3333
})
db.lost.save({
'_id': ObjectId('123456781234567812345678'),
'name': 3333,
'id':123412341234
})
Note that the _id length must be the same as the original, otherwise the save will fail
delete
delete all
delete only one
db.lost.remove({},{justOne:true})
comparison operation
Logical operations, separated by commas, indicate that a series of conditions must be met
Use or to indicate that one of the conditions in the array is satisfied.
set in, not range
Mixed, find results with id 111, 222 or id 333 and id not 111
The pit of range query will only find data smaller than 20
Custom query, not recommended, very slow
Regular matching, query the data starting with 2 in the specified range
limit skip completes paging, skip is the specified number of skips in the query results
Specifies the returned fields. _id is displayed by default, if it is not set, it means not displayed. If the field is set to 1, it means display.
sortsort
To count the number, use count, or omit find
deduplication
distinct('de-duplicated field', query condition)
Aggregation function, grouping documents, _id means, the field used for grouping, the number after sum means adding one each time there is a row
Count the sum of a field
The use of pipelines, first matching, then grouping, and pushing the data document into the specified field
Sort and specify display fields
View query plan
Build an index, 1/-1 indicates order or descending order
db.collection.ensureIndex({property, 1, -1})
