Lets say I have main table Users and a reference table UserRoles such that each User has one Role saved in the column roleId, and every role has an id and a description.
If I want to insert a new User with the role Administrator, the following SQL query would work:
INSERT INTO `users` (`name`, `roleId`)
VALUES ('John Doe', (SELECT `id` FROM `roles` WHERE `roles`.`description` = 'admin'));
How would I replicate the same in TypeORM having two entities User and Role?
I know I can do the following:
const adminRole = await Role.findOne({description: 'admin'});
const newUser = User.create({name: 'John Doe'});
newUser.role = adminRole;
await newUser.save();
But this would rather be equivalent to SELECT the role into a variable and then using that variable during the INSERT. is there a way to condense this into one query so that the database is hit only once?
I know that I can create an user with the relation like this
User.create({name: 'John Doe', role: {id: 1}});
But I need to know the id for this. If I put the name like the following
User.create({name: 'John Doe', role: {name: 'admin'}});
I get the following error Error: Cannot find alias for relation at type because I have not loaded the relation.
I've found information on how to make an INSERT INTO SELECT statement here, but this is where the whole insert comes from a select, not just a particular column.
Is there a way to emulate this query for insertions? or I'm forced to either do it in two steps (or as many as reference columns as I have) or use the query builder?
Thanks you in advance
Related
I am using Sequelize in my node js server. I am ending up with validation errors because my code tries to write the record twice instead of creating it once and then updating it since it's already in DB (Postgresql).
This is the flow I use when the request runs:
const latitude = req.body.latitude;
var metrics = await models.user_car_metrics.findOne({ where: { user_id: userId, car_id: carId } })
if (metrics) {
metrics.latitude = latitude;
.....
} else {
metrics = models.user_car_metrics.build({
user_id: userId,
car_id: carId,
latitude: latitude
....
});
}
var savedMetrics = await metrics();
return res.status(201).json(savedMetrics);
At times, if the client calls the endpoint very fast twice or more the endpoint above tries to save two new rows in user_car_metrics, with the same user_id and car_id, both FK on tables user and car.
I have a constraint:
ALTER TABLE user_car_metrics DROP CONSTRAINT IF EXISTS user_id_car_id_unique, ADD CONSTRAINT user_id_car_id_unique UNIQUE (car_id, user_id);
Point is, there can only be one entry for a given user_id and car_id pair.
Because of that, I started seeing validation issues and after looking into it and adding logs I realize the code above adds duplicates in the table (without the constraint). If the constraint is there, I get validation errors when the code above tries to insert the duplicate record.
Question is, how do I avoid this problem? How do I structure the code so that it won't try to create duplicate records. Is there a way to serialize this?
If you have a unique constraint then you can use upsert to either insert or update the record depending on whether you have a record with the same primary key value or column values that are in the unique constraint.
await models.user_car_metrics.upsert({
user_id: userId,
car_id: carId,
latitude: latitude
....
})
See upsert
PostgreSQL - Implemented with ON CONFLICT DO UPDATE. If update data contains PK field, then PK is selected as the default conflict key. Otherwise, first unique constraint/index will be selected, which can satisfy conflict key requirements.
I'm writing a nodejs application which users can buy products . I have a mysql database and sequelize. I have an object like this:
const Data = {
TransID,
TransTime,
Amount: TransAmount,
BillRefNumber,
MSISDN,
FirstName,
MiddleName,
LastName,
ShortCode: BusinessShortCode,
};
For any new transactions, I would like to check, using the TransId, whether this transaction exists in my table using the TransId . What is the best way to achieve this?
Maybe one of the best ways is to add a unique attribute to the TransID field in the database table. When you insert it, add a try-catch. It will catch an error if the same TransID already exists in the database. All you have to do is display the error.
I am fetching id column value from database for a particular email. In this case I am passing email and want to get primary key i.e id. This operation is successful as I get object which contains Object with the right and expected result. However I am not able to access the object.
I am receiving object like this:
[ UserInfo { id: 21 } ]
And I am not able to access id part of it.
I am using node.js, postgres for database and typeorm library to connect with database.
const id = await userRepo.find({
select:["id"],
where: {
email:email
}
});
console.log(id)
This prints the above object.
The id I am getting is right. But I am not able to retrieve the id part of the object. I tried various ways for e.g.
id['UserInfo'].id, id.UserInfo.
Please help me in accessing the object I am receiving
Typeorm .find() returns an array of objects containing entries corresponding to your filters, in your case, all entries with an email field corresponding to the email you specified.
Because the result is an array, you can access it this way:
const records = await userRepo.find({
select: ['id'],
where: {
email,
},
})
console.log(records[0].id)
You could also use the .findOne() method, which returns a single element and might be a better solution in your case :)
When you are putting a field in the select part select:["id"], you are only retrieving this part of the database.
It is like your query was this: select id from userRepo where email = email
and you need to put * in the select part to retrieve all the information:
const id = await userRepo.find({
select:["*"],
where: {
email:email
}
});
I am configuring Mongoose to work on an existing MongoDB, that has these two collections:
Users - with fields:
_id: ObjectId
name: String
org_id: ObjectId
Organizations - with fields:
_id: ObjectId
name: String
I want to be able to populate a User document by Organization data.
So I've created these two Models:
const userSchema = new Schema({
name: String,
org_id: {
type: Schema.Types.ObjectId,
ref: 'Organization',
},
});
const User = mongoose.model('User', userSchema);
const organizationSchema = new Schema({
name: String,
code: String,
});
const Organization = mongoose.model('Organization', organizationSchema);
Since historically the ref field from User to Organization is called org_id (instead of just organization) the population of a user by the organization code is:
const user = await User.findById('5b213a69acef4ac0f886cdbc')
.populate('org_id')
.exec();
where user.org_id will be populated by Organization data. Of course I would be happier to have organization instead of org_id in both - populate method and the path (i.e. user.organizationd).
What is the proper way to achieve it without changing the existing documents?
I could create my Schema methods (instead of populate) and aliases, but I am looking for a more generic and elegant solution.
I understood that you don't want to change the existent documents, but for me, if this name of field doesn't make more sense you need to refactor.
Change the name of the field, organization instead of org_id.
For this you can use the $rename command: MongoDB $rename
db.getCollection('users').updateMany({},{$rename: { "org_id": "organization" }});
After this you will can call .populate('organization').
If it is impossible, I believe that you will not find a solution better than aliases.
Mongoose Documentation: Aliases
I will follow along your code.looks like you applied this: mongoose.Schema=Schema
you embedded Organization model into User. first lets extract organization details for each user.
//import User and Organization models
const main=async ()=>{
const user=await User.findById("placeUserId")//we get the user
const populated=await user.populate("org_id").execPopulate()//we populated organization with all properties
console.log(populated.org_id) }
in the above code, org_id was already referenced in the userSchema. we just reached org_id property and extracted. this was simple. next without changing any code in userSchema and organizationSchema i will find which user is in which organization with virtual property.
virtual property allows us to create virtual fields in the database. it is called virtual because we do not change anything. it is just a way that to see how two models are related.
for this we are gonna add a little code on the page where you defined you defined your organizationSchema file which i assume in models/organization.js. this code will describe the virtual field. it is kinda schema of the virtual field.
//models/organization.js
organizationSchema.virtual('anyNameForField',{
ref:"User", //Organization is in relation with User
localField:"_id"//field that Organization holds as proof of relation
foreignField:"org_id"//field that User holds as proof of relation
})
now time to write the function to find the user inside the organization.
const reverse=async ()=>{
const organization=await Organization.findById("")
const populated=await organization.populate("anyNameForField").execPopulate()
console.log(populated.anyNameForField) //i gave a stupid name to bring your attention.
}
very simple and elegant!
I have a product which is owned by a user in my CouchDB.
product =
name: 'Laptop'
userId: somelongid
user =
username: 'James'
With views and include_docs=true it returns:
product =
name: 'Laptop'
user =
username: 'James'
( I know it doesn't exactly return the above but it's close enough )
I do this cause every time I need a product I also need the owner (to link to his page). At first I thought I would just use include_document=true on the _change feed but of course that does something else.
So how can I get the related user when getting product results?
One solution is to collect all the userIds from the search result and query the _all_docs view in couchDb to get the users.
use a view (f.E. "userByDocId") that emits (doc._id,doc.user)
and do a query userByDocId?key="Username"