How can I prevent duplication of records with the same combinations of entities, here : id_product and id_customer. When I click "save relation" a relation (many-to-many) between product and customer is created and this relation has its own id, id_product and id_customer. Is there any solution to block creation of relation between product and customer if such combination already exists in MySQL database ?
public saveRelation = (relationFormValue) => {
const newRelation = {
id_product: relationFormValue.id_product ,
id_customer: relationFormValue.id_customer
};
const dialogRef = this.dialog.open(ConfirmDialogComponent, {
maxWidth: "400px",
data: new ConfirmDialogModel("Please confirm",'Are you sure to save this relation ?')
});
dialogRef.afterClosed().subscribe(dialogResult => {
if (dialogResult==true) {
this.relationService.create(newRelation)
.subscribe(
response => {
this.dialogRef.close(true);
},
error => {
this.errorService.handleError(error);
});
}
});
}
Related
I am working on a CRUD application with Sequelize and ExpressJS that has the following tables:
Parents
Students
ParentStudents
id
id
id
name
name
idParent
idStudent
I want to query the Parents table and have students key created by a left join between students and ParentStudents on idParent;
I want to get data in the following way:
{
"data":[
{
"name":"nameParent2",
"students":[
{
"name":"Student1"
},
{
"name":"Student2"
}
]
},
{
"name":"nameParent2",
"students":[
{
"name":"Student1"
},
{
"name":"Student2"
}
]
}
]
}
I tried something like this, but is wrong and giving data from ParentStudents:
models.parents.findAll({
include: [{
model: models.parentStudents
}]
}).then(data => {
res.json({
message: "Hello from server!!!",
data: data
});
});
Like this is failing to make the association between Students and ParentStudents. (students is not associated to parentStudents!)
models.parents.findAll({
include: [{
model: models.parentStudents,
include: [{
model: models.students
}]
}]
}).then(data => {
res.json({
message: "Hello from server!!!",
data: data
});
});
My relationships are done like this:
db.parents.hasMany(db.parentStudents);
db.students.hasMany(db.parentStudents);
I also tried Many-to-Many, but still doesn't work:
db.students.belongsToMany(db.parents, { through: db.parentStudents });
db.parents.belongsToMany(db.students, { through: db.parentStudents });
Does someone know how this can be done?
One workaround is:
let parents = await models.parents.findAll();
for (let parent of parents) {
let idParent = parent.dataValues.id;
let students = await models.sequelize.query(`
SELECT * FROM students s
LEFT JOIN parentStudents ps
ON s.id = ps.studentId
WHERE ps.parentId =${idParent};
`);
parent.dataValues['students'] = students;
}
I need to check if entry with specific ID exists in the database using Sequelize in Node.js
function isIdUnique (id) {
db.Profile.count({ where: { id: id } })
.then(count => {
if (count != 0) {
return false;
}
return true;
});
}
I call this function in an if statement but the result is always undefined
if(isIdUnique(id)){...}
I don't prefer using count to check for record existence. Suppose you have similarity for hundred in million records why to count them all if you want just to get boolean value, true if exists false if not?
findOne will get the job done at the first value when there's matching.
const isIdUnique = id =>
db.Profile.findOne({ where: { id} })
.then(token => token !== null)
.then(isUnique => isUnique);
Update: see the answer which suggests using findOne() below. I personally prefer; this answer though describes an alternative approach.
You are not returning from the isIdUnique function:
function isIdUnique (id) {
return db.Profile.count({ where: { id: id } })
.then(count => {
if (count != 0) {
return false;
}
return true;
});
}
isIdUnique(id).then(isUnique => {
if (isUnique) {
// ...
}
});
You can count and find.
Project
.findAndCountAll({
where: {
title: {
[Op.like]: 'foo%'
}
},
offset: 10,
limit: 2
})
.then(result => {
console.log(result.count);
console.log(result.rows);
});
Doc link, v5 Beta Release
I found the answer by #alecxe to be unreliable in some instances, so I tweaked the logic:
function isIdUnique (id, done) {
db.Profile.count({ where: { id: id } })
.then(count => {
return (count > 0) ? true : false
});
}
As Sequelize is designed around promises anyway, alecxe's answer probably makes most sense, but for the sake of offering an alternative, you can also pass in a callback:
function isIdUnique (id, done) {
db.Profile.count({ where: { id: id } })
.then(count => {
done(count == 0);
});
}
}
isIdUnique(id, function(isUnique) {
if (isUnique) {
// stuff
}
});
Extending #Jalal's answer, if you're very conscious about performance implications while maintaining a simple Sequelize structure and you do not need the row data, I suggest you only request one column from the database. Why waste bandwidth and time asking the database to return all columns when you won't even use them?
const isIdUnique = id =>
db.Profile.findOne({ where: { id }, attributes: ['id'] })
.then(token => token !== null)
.then(isUnique => isUnique);
The attributes field tells Sequelize to only request the id column from the database and not sending the whole row's content.
Again this may seem a bit excessive but at scale and if you have many columns that hold a lot of data, this could make a giant difference in performance.
Try the below solution. I tried it and it works well.
const isIdUnique = async (id, model) => {
return await model.count({ where: { id: id } });
};
const checkExistId = await isIdUnique(idUser, User);
console.log("checkExistId: ", checkExistId);
I'm building a rest api that uses Sequelize to interact with the database. A query looks like this:
function read_category(req, res) {
Category.findById(req.params.categoryId, {rejectOnEmpty: true}).then(category => {
res.json(category);
}).catch(Sequelize.EmptyResultError, function () {
res.status(404).json({message: 'No category found'});
}
).catch(function (err) {
res.send(err);
}
);
}
Now I want the category object that is returned from Sequelize and then returned to the user to include the linkto the ressource. I could do:
category.dataValues.link = config.base_url + 'categories/' + category.dataValues.id;
Which would result in:
{
"id": 1,
"name": "TestCategory 1",
"position": 1,
"createdAt": "2018-08-19T11:42:09.000Z",
"updatedAt": "2018-08-19T11:42:09.000Z",
"link": "http://localhost:3000/categories/1"
}
Since I have more routes than this one I'm wondering if there's a dynamic way to add the link property to every category. I don't want to save it in the database because the base-url might differ.
Thanks!
Better way to do it is , create a getter method :
const Category = sequelize.define( 'category' , {
....
your_fields
....
},
{
getterMethods:{
link() {
return config.base_url + 'categories/' + this.id;
}
}
});
module.exports = Category;
Then
Category.findAll(...).then(categories => {
// Now there is no need to append data manually , it will added each time when you query
console.log(categories); // <-- Check the output
})
I'm building an application with express and i'm using bookshelf (mysql) js as ORM.
I have a relation many-to-many and i'm trying to store in the joining table some additional data.
My models:
const Product = Bookshelf.Model.extend({
tableName: 'products',
factors() {
return this.belongsToMany('Factor', 'product_factors', 'product_id', 'factor_id')
}
})
const Factor = Bookshelf.Model.extend({
tableName: 'factors',
products() {
return this.belongsToMany('Product')
}
})
Creating new product with relations in 'product_factors' table.
/** Create product */
router.route('/').post((req, res) => {
new Product({name: req.body.name})
.save()
.then(product => {
// attaching relation
product.factors().attach([3, 5])
.then(hz => {
res.status(201).json({
message: 'Product created'
})
})
})
})
The 'product_factors' table
|ID|product_id|factor_id|quantity|
|--|----------|---------|--------|
|1 |10 |3 |NULL |
|2 |10 |5 |NULL |
How can i insert quantity at the same time with attaching relations?
The documentation has an example of how to do that in the model.belongsToMany() section. For convenience here it is:
let Doctor = bookshelf.Model.extend({
patients: function() {
return this.belongsToMany(Patient).through(Appointment);
}
});
let Appointment = bookshelf.Model.extend({
patient: function() {
return this.belongsTo(Patient);
},
doctor: function() {
return this.belongsTo(Doctor);
}
});
let Patient = bookshelf.Model.extend({
doctors: function() {
return this.belongsToMany(Doctor).through(Appointment);
}
});
As you can see in the Doctor and Patient models you must use the .belongsToMany(Model).through(AnotherModel). Then it's just a matter of using the attach(), detach(), updatePivot() and withPivot() methods as needed to handle the data.
Also, since you're defining the joining model you can also use it directly to access and modify the data that related table contains. For example:
Appointment.forge({patient_id: 2, doctor_id: 1, confirmed: true}).save()
or
Appointment.forge({id: 4}).destroy()
I'm newbie with Sails/WaterLine ORM
I'm following http://sailsjs.org/documentation/concepts/models-and-orm/associations/through-associations
One question.
How way to insert data into a join table ?
For example: User m - m Pet
User model
module.exports = {
attributes: {
name: {
type: 'string'
},
pets:{
collection: 'pet',
via: 'owner',
through: 'petuser'
}
}
Pet model
module.exports = {
attributes: {
name: {
type: 'string'
},
color: {
type: 'string'
},
owners:{
collection: 'user',
via: 'pet',
through: 'petuser'
}
}
PetUser model (join table)
module.exports = {
attributes: {
owner:{
model:'user'
},
pet: {
model: 'pet'
}
}
}
Pet data is available (some record with ID1, ID2, ID3...)
I want to add new one user with some pets
PetUser ( id , id_of_user, id_of_pet)
1, U1, P1
2, U1, P2
{
"name" : "John",
"pets" : [2,3]
}
UserController
module.exports = {
addUserWithPets: function(req, res) {
User.create(req.body).exec(function(err, user) {
if(err){
throw err;
}else {
/*pets.forEach(function(pet, index){
user.pets.add(pet);
})
user.save(function(err) {});*/
user.pets.add(data);
user.save(function(err) {});
}
return res.ok({
data: user
});
})
}
};
Thanks!
I think this hasn't been implemented yet in sails.
Refer to this question: through associations in sails.js on SO.
Here is what waterline docs say:
Many-to-Many through associations behave the same way as many-to-many associations with the exception of the join table being automatically created for you. This allows you to attach additional attributes onto the relationship inside of the join table.
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