Mongodb updates update
1.$inc
Usage: {$inc: {field:value}}
Function: add value to a field in a numeric field
> db.test1.update ({'name':'wang'}, {$inc: {age:1}})
> db.test1.find ({'name':'wang'})
{"_ id": ObjectId ("58662477fb6a734e8f45133f"), "name": "wang", "age": 20, "sex": "M"}
2.$set
Usage: {$set: {field:value}}
Function: set the value of a field field in the document to value
> db.test1.update ({'name':'wang'}, {$set: {' sex':'F'}})
> db.test1.find ({'name':'wang'})
{"_ id": ObjectId ("58662477fb6a734e8f45133f"), "name": "wang", "age": 20, "sex": "F"}
3.$unset
Usage: {$unset: {field:1}}
Function: delete a field field
> db.test1.update ({'name':'wang'}, {$unset: {' sex':1}})
> db.test1.find ({'name':'wang'})
{"_ id": ObjectId ("58662477fb6a734e8f45133f"), "age": 20, "name": "wang"}
4.$push
Usage: {$push: {field:value}}
Function: append value to field. Note: field can only be an array type. If field does not exist, an array type will be inserted automatically.
> db.test1.update ({'name':'wang'}, {$push: {' sex':'F'}})
> db.test1.update ({'name':'wang'}, {$push: {' sex':'M'}})
> db.test1.find ({'name':'wang'})
{"_ id": ObjectId ("58662477fb6a734e8f45133f"), "age": 20, "name": "wang", "sex": ["F", "M"]}
5.pushAll
Usage: {$pushAll: {field:value_array}}
What it does: use the same as $push, except that $pushAll can append more than one value to an array field at a time.
> db.test1.update ({'name':'wang'}, {$pushAll: {' sex': ['M or Fundation recorder M and F']}})
> db.test1.find ({'name':'wang'})
{"_ id": ObjectId ("58662477fb6a734e8f45133f"), "age": 20, "name": "wang", "sex": ["F", "M", "M or F", "M and F"]}
> db.test1.update ({'name':'wang'}, {$push: {' sex': ['M or Fundation recorder M and F']}})
> db.test1.find ({'name':'wang'})
{"_ id": ObjectId ("58662477fb6a734e8f45133f"), "age": 20, "name": "wang", "sex": ["F", "M", "M or F", "M and F", ["M or F", "M and F"]]}
6.$addToSet
Usage: {$addToSet: {field:value}}
What it does: add a value to the array and increase it only if the value does not exist in the array.
> db.test1.update ({'name':'wang'}, {$addToSet: {' sex': ['M or Flowers']}})
> db.test1.find ({'name':'wang'})
{"_ id": ObjectId ("58662477fb6a734e8f45133f"), "age": 20, "name": "wang", "sex": ["F", "M", "M or F", "M and F", ["M or F", "M and F"], ["M or F", "MF"]]}
7.$pop
Usage: delete the first value in the array: {$pop: {field:-1}}, delete the last value in the array: {$pop: {field:1}}
Function: used to delete a value in an array
> db.test1.find ({'name':'wang'})
{"_ id": ObjectId ("58662477fb6a734e8f45133f"), "age": 20, "name": "wang", "sex": ["F", "M", "M or F", "M and F"]}
> db.test1.update ({'name':'wang'}, {$pop: {' sex':1}})
> db.test1.find ({'name':'wang'})
{"_ id": ObjectId ("58662477fb6a734e8f45133f"), "age": 20, "name": "wang", "sex": ["F", "M", "M or F"]}
8.$pull
Usage: {$pull: {field:_value}}
Function: delete a value equal to _ value from the array field
> db.test1.update ({'name':'wang'}, {$pull: {' sex': "F"}})
> db.test1.find ({'name':'wang'})
{"_ id": ObjectId ("58662477fb6a734e8f45133f"), "age": 20, "name": "wang", "sex": ["M", "M or F"]}
10.$rename
Usage: {$rename: {old_field_name:new_field_name}}
Purpose: rename fields
> db.test1.update ({'name':'wang'}, {$rename: {' name':'names'}})
> db.test1.find ({'name':'wang'})
> db.test1.find ({'names':'wang'})
{"_ id": ObjectId ("58662477fb6a734e8f45133f"), "age": 20, "names": "wang", "sex": ["M", "M or F"]}
