MongoDB Inner join using aggregate and lookup
--
Below is the sample query with explanations :-
Collection1Name.aggregate([
{ “$match”: { “Id”: new mongoose.Types.ObjectId(req.params.id) } },
{ $lookup:
{
from: ‘Collection2Name’,
localField: ‘localfieldName’,
foreignField: ‘foreignfieldName’,
as: ‘info’
}
}, {
$unwind: “$info”,
},
]).exec((err, result)=>{
if (err) {
console.log(“error” ,err)
}
if (result) {
console.log(‘zx zxcz’,result);
}
});
$match — This will match/filter your data base on id or some values
Collection1Name — Please specify collection1name. So for e.g If you have imported collection like this const TableName1= require(‘../models/collection’); then you can mention TableName1
Collection2Name — Please specify collection2name . So for e.g If you have imported collection like this const TableName= require(‘../models/collection’); then you can mention tablenames
localField — Please specify local field name from Collection1Name
foreignField — Please specify foreign filed name from Collection2Name
$unwind — To deconstruct it into a sub-document
