如何在mongodb中的对象数组中搜索 [英] How to search in array of object in mongodb
问题描述
Suppose the mongodb document(table) 'users' is
{
_id: 1,
name: {
first: 'John',
last: 'Backus'
},
birth: new Date('Dec 03, 1924'),
death: new Date('Mar 17, 2007'),
contribs: ['Fortran', 'ALGOL', 'Backus-Naur Form', 'FP'],
awards: [
{
award: 'National Medal',
year: 1975,
by: 'NSF'
},
{
award: 'Turing Award',
year: 1977,
by: 'ACM'
}
]
}
// ...and other object(person)s
I want to find the person who has the award 'National Medal' and must be awarded in year 1975 There could be other persons who have this award in different years.
How can I find this person using award type and year. So I can get exact person.
The right way is:
db.users.find({awards: {$elemMatch: {award:'National Medal', year:1975}}})
$elemMatch
allows you to match more than one component within the same array element.
Without $elemMatch
mongo will look for users with National Medal in some year and some award in the year 1975, but not for users with National Medal in 1975.
See MongoDB $elemMatch Documentation for more info. See Read Operations Documentation for more information about querying documents with arrays.
这篇关于如何在mongodb中的对象数组中搜索的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!