Some simple MongoDB common command collection

1. $all means to match an array with multiple elements
2. $slice specify the offset value and the number of elements you want to return
Db.user.find (aa,{"common": {"$slice": 10}})


3. Db.user.ensureIndex ({"Name": 1})
Add index
4. Db.user.drop () Delete collection
5. Db.user.remove () Remove the data in the collection, you need to add query


6. Use Db.user.find (). Hint ({"username": 1}) to force an index to query using hint
7. Db.user.ensureIndex ({"username": 1},{"unique": true}) Create a unique index
8. Db.user.getIndexes () View index information in a given collection


9. Db.user.aggregate ({$group: {"_id": {"date": "$date", "NUMA": "$numa"}});
Db.getcollectionnames (); Query all collection names under the library table


One. Show collections; View database under Collection commands
Show DBS; View Database Commands