How to realize the query of connected tables in mongodb

Today, I will talk to you about how to achieve linked table query in mongodb, many people may not know much about it. In order to make you understand better, the editor has summarized the following content for you. I hope you can get something according to this article.

1.mongodb regular matching

/ * use the $regex field to match * / name: {$regex: 'aa', $options:' i'}; or: name: {$regex: / aa/, $options:'i'}; or: name: {$regex: / aa/i}; / * directly use the expression * / name: {/ aa/i} / * use the $in to match, this field must be an array * / name: {$in: [/ aa/]}

two。 Connected table query

Use $lookup to query connected tables

/ * aggregate aggregation operation: $unwind splits the array into individual elements * $group grouping filters the returned values based on * $sum statistics * $project Whether to return a filtered field * $match matching condition * * / usingRecord.aggregate ([{$lookup: {from: 'resources', / * the name of the table to be connected * / localField:' resource_id', / * the field corresponding to the current table * / foreignField:'_ id' / * the field of the table to be joined * / as: 'resourceInfo' / * the field name displayed in the query result * /},}, {$match: {' user_id': user_id}}, {$unwind:'$resourceInfo'}, {$sort: {_ id:-1}}])

3. Summary

Mongodb database is a non-relational, document-based database. Storing associated data in a document can reduce the number of associated queries between tables.

I first look for materials on the Internet to learn, and then I have a lot of feelings when learning the videos on the Mu course net. At present, there is still some confusion. I will find a better way to insert the data.

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