Good day all, can someone suggest me which async function should i use?,
in my case, I need an output the 1st member of each group.
*** note this is just a example of the flow of my program.
/*
Grouplist groupmember
Id | name id | name | group
1 | group1 1 | John | 1
2 | group2 2 | James | 1
3 | group3 3 | Paul | 3
4 | Angel | 2
5 | Anne | 2
6 | Jane | 3
looking for output like this
id | name | group
1 | John | 1
4 | Angel | 2
3 | Paul | 3
*/
var name = [];
Grouplist.find( function(err, grouplist){
for(var x=0;x<=grouplist.length-1; x++){
groupmember.find({id:grouplist[x].id}).limit(1).exec(
function callBack(err,results){
if(err) console.log(err);
name[x] = results.name;
})
}
})
You can get the result in one query using mongodb aggregate operators:
groupmember.aggregate(
[
{
$group:
{
_id: "$group", //grouping key
member: { $first: "$$CURRENT" } //return the first matched document
}
},
{
$project : //project the document to top-level
{
_id: "$member._id",
name: "$member.name",
group: "$member.group"
}
}
],
function(err, members){
console.log(members)
}
)
Related
I'm using postgresql and sequelize to do my db operations
Suppose I have a person table like this:
id (pkey) | name | email (unique) | company
1 | john | john#x.com | abc
2 | mary | mary#y.com | abc
3 | will | NULL | xyz
I make the unique constraint like this:
const PersonData = sequelize.define(
'users',
{
....
email: {
type: Sequelize.STRING,
allowNull: false,
unique: {
args: true,
msg: 'Email already in use!',
},
},
....
},
I'm getting payload like
{{
id: 1,
email: mary#y.com
},
{
id: 2,
email: john#x.com
}}
I want to swap the emails for id 1 and id 2 here. How can I do that using sequelize?
The output I want:
id (pkey) | name | email (unique) | company
1 | john | mary#y.com | abc
2 | mary | john#x.com | abc
3 | will | NULL | xyz
I am creating a social web using Node js and mongoDB. I have three tables as events, projects and reactions(like, comment).
Every event has many projects and every project has many reactions.
events
|----|---------|-------------|
| id | title | description |
|----|---------|-------------|
| e1 | event 1 | |
| e2 | event 2 | descc |
| e3 | event 3 | |
|----|---------|-------------|
projects
|----|-----------|-------------|----------|
| id | project | description | event_id |
|----|-----------|-------------|----------|
| p1 | project 1 | sample | e1 |
| p2 | project 2 | sample | e1 |
| p3 | project 3 | sample | e1 |
| p4 | project 1 | sample | e2 |
|----|-----------|-------------|----------|
reactions
|----|----------|------------|----------|--------|-------|
| id | user_id | project_id | event_id | type | value |
|----|----------|------------|----------|--------|-------|
| 1 | user1 | p1 | e1 | comment| nice |
| 2 | user1 | p1 | e1 | comment| wow |
| 3 | user2 | p1 | e1 | like | 1 |
| 4 | user2 | p1 | e2 | comment| good |
| 5 | user1 | p2 | e1 | comment| nice |
| 6 | user3 | p1 | e1 | comment| nice |
| 7 | user4 | p1 | e1 | like | 1 |
| 8 | user4 | p1 | e1 | comment| bad |
| 9 | user5 | p2 | e1 | comment| enjoy |
| 10 | user3 | p2 | e1 | comment| happy |
|----|----------|------------|----------|--------|-------|
my code
try
{
const id = req.params.id;
var ObjectId = require('mongodb').ObjectID;
if(!ObjectId.isValid(id))
{
return res.status(503).json("Invalid ID");
}
var aggregate = Event.aggregate();
aggregate.match({"_id":ObjectId(id)})
.lookup({ from: "pojects", localField: "_id", foreignField: "event_id",as: "project_doc"})
.lookup({from: "user_reactins", localField: "_id", foreignField: "event_id", as: "reactions"})
.lookup({from: "user_reactins", localField: "project_doc._id", foreignField: "project_id", as: "pro_reactions"})
.addFields({"project_doc.totalComments": "$pro_reactions"})
.project({_id:"$_id",title:"$title", project_doc:"$project_doc",
total_like_event: {
"$size": {
$filter: {
input: "$reactions",
as: "s",
cond: {
$eq: ["$$s.key", "like"]
},
}
}
},
total_comment_event: {
"$size": {
$filter: {
input: "$reactions",
as: "s",
cond: {
$eq: ["$$s.key", "comment"]
},
}
}
}
})
var options = {}
Event.aggregatePaginate(aggregate, options, function(err, results, pageCount, count)
{
return res.status(200).json({data:results[0],pro_status:statusResult,eve_status:eveResult,eve_cat:categoryResult});
})
}
catch (err)
{
return res.status(500).json(err);
}
this is my end point http://url/api/events/e1
If I used this end point, I want all comments for the given event(e1) by categorized by project as follows
{
"data": {
"_id": "e1",
"title": "event 1",
"project_doc": [
{
"_id": "p1",
"title": "project 1",
"description": "sample",
"totalComments": [
{
"_id": "1",
"user_id": "user1",
"programme_id": "p1",
"key": "comment",
"value": "nice",
},
{
"_id": "2",
"user_id": "user1",
"programme_id": "p1",
"key": "comment",
"value": "wow",
},
{
"_id": "6",
"user_id": "user3",
"programme_id": "p1",
"key": "comment",
"value": "nice",
},
{
"_id": "1",
"user_id": "user1",
"programme_id": "p1",
"key": "comment",
"value": "nice",
}
]
},
],
"total_view_event": 0,
"total_like_event": 1,
"total_comment_event": 4
}
}
i am new at MERN stack
i tried to write this query but i can't and search a lot on google without any solution
i have to table one for posts and the second for categories
table 1 posts
--------------------------
|id | title | category |
--------------------------
| 1 | title1 | 1 |
| 2 | title2 | 2 |
| 3 | title3 | 1 |
| 4 | title4 | 1 |
=================
table 2 categories
---------------
|id | name |
---------------
| 1 | cat1 |
| 2 | cat2 |
====================
the results i want is this
---------------------------------
|id | name | number of posts |
---------------------------------
| 1 | cat1 | 3 |
| 2 | cat2 | 1 |
if it's can a help i write this query in mysql
SELECT categories.*,COUNT(posts.id) AS np FROM `categories` JOIN materials ON (categories.id = posts.category) GROUP BY categories.id
and thank you
You can try below aggregation in mongodb 3.6 and above
db.collection.aggregate([
{ "$lookup": {
"from": "posts",
"let": { "id", "$id" },
"pipeline": [
{ "$match": { "$expr": { "$eq": ["$category", "$$id"] }}},
{ "$count": "count" }
],
"as": "count"
}},
{ "$project": {
"name": 1,
"numberOfPosts": { "$arrayElemAt": ["$count.count", 0] }
}}
])
I need to get record by price range but the query is working fine in shell but not in nodejs. Here is query:
db.model.aggregate([
{ $match: { make_id: make_id } },
{
$lookup: {
from: 'variants',
localField: '_id',
foreignField: 'model_id',
as: 'variant_list'
}
},
{
$unwind: {
path: '$variant_list',
preserveNullAndEmptyArrays: false
}
},
{$match: {status:1, $and:[{'variant_list.price': {$lte:Number(max_price)}}]}},
{$project: { make_id: 1, model_name: 1, variant_list: '$variant_list'}}
])
I have checked the price in database. it is stored like NumberInt(300000) and in my query i have parsed in integer type like => max_price to Number(max_price).
and it gives me all record which are less than and equal to 300000 but it also gives the record which are less than 400000.
But If i'm not using aggregate framework then it is giving me perfect result:
db.model.find({status:1, $and:[{'variant_list.price': {$lte:Number(max_price)}}]})
I dont know why $lte not working perfectly with aggregate and $lookup.
Please Help!!
Updated Sample Collection and Documents
MakeId = a123;
Models:
-----------------------------
mid | makeid | model |
-----------------------------
m1 | a123 | MDLi1 |
m2 | a123 | MDLi2 |
m3 | a123 | MDLi3 |
m4 | a123 | MDLi4 |
m5 | a123 | MDLi5 |
-----------------------------
Variants:
----------------------------------------
vid | modelid | variants | price |
----------------------------------------
v1 | m1 | VARi1 | 150000 |
v2 | m1 | VARi2 | 250000 |
v3 | m1 | VARi3 | 300000 |
v4 | m1 | VARi4 | 350000 |
v5 | m1 | VARi5 | 380000 |
v6 | m2 | VARi6 | 250000 |
v7 | m2 | VARi7 | 280000 |
v8 | m2 | VARi8 | 380000 |
v9 | m2 | VARi9 | 400000 |
v10 | m2 | VARi10 | 450000 |
----------------------------------------
I need to get model detail and variants list by variant price like price range should be between 0 to 300000
My Desire result is :
{
"data": [
{
"makeid": "a123",
"modelid": "m1",
"variant_list": [
{
"variant_id": "v1",
"variant_name": "VARi1",
"price": 150000
},
{
"variant_id": "v2",
"variant_name": "VARi2",
"price": 250000
},
{
"variant_id": "v3",
"variant_name": "VARi3",
"price": 300000
}
]
},
{
"makeid": "a123",
"modelid": "m2",
"variant_list": [
{
"variant_id": "v6",
"variant_name": "VARi6",
"price": 250000
},
{
"variant_id": "v7",
"variant_name": "VARi7",
"price": 280000
}
]
}
]
}
Using the example given on the Sails.js documentation page, I get the following error : "Maximum call stack size exceeded error".
items.find().populate("user", {name:givenName}).exec(function(err, response) {
console.log(response);
}
The matter is that when I look with wireshark, the query on the database tries to find every user (and the database is big), but it doesn't make any join.
items
+-----------+--------------+------+-----+
| Field | Type | Null | Key |
+-----------+--------------+------+-----+
| id | int(6) | NO | PRI |
| name | varchar(255) | NO | |
+-----------+--------------+------+-----+
user
+-----------+--------------+------+-----+
| Field | Type | Null | Key |
+-----------+--------------+------+-----+
| id | int(6) | NO | PRI |
| name | varchar(255) | NO | |
| item_id | int(11) | YES | MUL |
+-----------+--------------+------+-----+
Should be as simple as:
items
.find()
.populate("user")
.where({name: givenName}) //or .where({user: {name: givenName}})
.exec(function(err, response) {
console.log(response);
});
Ok, If like you said you want only items for a specific user do this :
user.findOneByName(givenName).exec(function(err, user) {
items.find().where({user : user.id}).exec(function(err, response) {
console.log(response);
});
});