mongodb database basics associated with table queries

preface

When I was working on my own project, I still kept the influence of the non-relational DATABASE of mongodb and the relational database in my mind at the very beginning. I always wanted to conduct a linked table query, and then Read the official website and materials to learn about it. In addition, I used regularness to match the query, so I made a record here

1.mongodb regular matching

/*  use $regex Field matching  */
name: {$regex: 'aa', $options: 'i'};
 Or: 
name: {$regex: /aa/, $options: 'i'};
 Or: 
name: {$regex: /aa/i};
/*  Use expressions directly  */
name: {/aa/i}
/*  use $in To match, this field must be 1 An array  */
name: {$in: [/aa/]}

2. Connect table query

Use $lookup for the join table query

/* aggregate The aggregation operation, $unwind Split the array into individual elements 
 * $group  Group by 
 * $sum  statistical 
 * $project  Filter the return value to return a field after filtering 
 * $match  Matching conditions 
 * */
usingRecord.aggregate([
  {
   $lookup: {
    from: 'resources', /*  The name of the table to join  */
    localField: 'resource_id', /*  The field corresponding to the current table  */
    foreignField: '_id', /*  The field of the table to join  */
    as: 'resourceInfo' /*  The name of the field shown in the query result  */
   },
  },
  {
   $match: {
    'user_id': user_id
   }
  },
  {
   $unwind: '$resourceInfo'
  },
  {
   $sort: {
    _id: -1
   }
  }
 ])

3. Summary

The mongodb database is a non-relational, document database, and storing associated data in one document reduces the number of associated queries between tables
After learning online materials and then learning online videos of MOOCS, I felt a lot. At present, I am still a little confused. I will find a better way to achieve data insertion

conclusion