Imagine that I have a following query (I am using Apollo):
const userQuery = gql`
query {
user {
id
name
}
}
`;
I want to fetch name field only if some condition is met (let's say variable shouldFetchName is true). How should I approach this and what is the best practice?
You can pass a variable to your query and use a Directive to fetch a field conditionally, like name #include(if: $shouldFetchName).
See the docs for Directives.
Related
In GraphQL, is it possible to fetch data with a 'filtered' array (e.g. only with a single object) instead of an array with all the (multiple) objects? For instance, by providing the 'id' property for the selected object you want to get in the query.
If yes, what needs to be changed in the below query? Just wondering if this filtering can already be done server side.
const selectedId = 'n32j23h'
const query = gql`
query getData {
dataObj {
bigArray {
id
name
}
}
}
`;
Define a new query in your typeDefs:
query getDataById(id: ID!): returnObjectType
Implement a resolver for that query that uses the id parameter to filter your bigArray
In my app every customer has a own table for its data. Depending on which customer was selected I want to dynamically build the tablename for the Graphql query.
For example:
// Query for customer 1
gql`
query overviewQuery {
customer_1 {
aggregate {
count
}
}
}
`
// Query for customer 2
gql`
query overviewQuery {
customer_2 {
aggregate {
count
}
}
}
`
I have the customer id in my vuex store and want to insert a variable into the query like in the following pseudocode which is not working.
const tblUserAggregateName = `customer_${this.$store.state.customer.customerId`
gql`
query overviewQuery {
${this.tblUserAggregateName} {
aggregate {
count
}
}
`
Is there an option how to do this or how can this problem be solved?
It is not an option to hardcode all different customer queries and selected them on runtime.
Thanks!
In the answers it was mentioned, that it is against best practice to dynamically change the table name of GraphQL queries.
As changing the complete database structure for all clients (they each have a separate Database with a own PostgreSQL schema name) is not an option, I found a solution the looks a little bit hacky and definitely not best practice but I thought I might be interesting to share for others with the same problem.
The approach is pretty easy: I write the query as a simple string where I could use variables and convert them later to the gql AST Object with graphql-tag
const query = () => {
const queryString = `
{
${customerId}_table_name {
aggregate {
count
}
}
}`
return gql`${queryString}`
}
Works, but I you have a better solution, I am happy to learn!
You can supply variables, but they should not be used to dynamically infer schema object names. This violates core concepts of GraphQL. Try this instead:
gql`
query overviewQuery ($customerId: ID!) {
customerData (id: $customerId) {
tableName
aggregate {
count
}
}
}`
Apollo provides great documentation on how to supply variables into a query here: https://www.apollographql.com/docs/react/data/queries/
The backend can then use the customerId to determine what table to query. The client making requests does not need to know (nor should it) where that data is or how it's stored. If the client must know the table name, you can add a field (as shown in the example)
I'm trying to run a GraphQL query in the AWS AppSync console:
query MyQuery {
getUserInfoById(id: "1234566789") {
account {
id // need this value for getAvailableCourses
}
}
getAvailableCourses(accountId: "", pageNumber: 0) {
data {
id
name
type
}
}
}
Basically I need the value account.id in getUserInfoById for getAvailableCourses. I'm obviously new to GraphQL. How would I go about this?
To the best of my knowledge, there can be two ways you can do this.
You can handle this in your frontend by getting user's id
from the session info and pass it to the other query.
You can also merge these two queries and make it one. You will also have to change the respective fields. Then attach a resolver with AvailableCourses and use $ctx.source.id in the resolver to get further details. Schema would look something like this
type Account {
id : ID!
availableCourses: AvailableCourses
..
}
type AvailableCourses {
name: String!
type: String!
..
}
type Query {
getUserInfoById(id: ID!): Account
}
Using the returned fields as inputs for a second query into your datasource is precisely what field resolvers are for. I can't say for sure since I don't know your schema or access patterns but it looks like you need to make available courses a sub field of the user.
I'm looking to create a GraphQL query that selectively adds/removes fields based on a variable "type", which is a string:
query ResultsPage($casetype: String!)
According to the reference on Directives, you can use a boolean value to either #include or #skip certain fields:
query Hero($episode: Episode, $withFriends: Boolean!) {
hero(episode: $episode) {
name
friends #include(if: $withFriends) {
name
}
}
}
How could I do something similar with this string value? i.e. only include the friends field if $casetype = "foo". Is this possible with GraphQL?
Thanks!
Unfortunately there is no way to use string comparison. Only way that you can is write custom Directive which can handle on its own.
please check a closed issue here
How do you query using GraphQL in a manor similar to SQL's like operator?
Example: What users have a first name starting with jason?
select * from users where first_name like "jason%"
The short answer is: you don't.
The longer answer is that you have to write that code yourself. GraphQL isn't a database query language like SQL, it's an application query language. What that means is that GraphQL won't let you write arbitrary queries out of the box. It will only support the types of queries defined in your GraphQL schema.
If you want to be able to write a query that contains like, you have to
a) declare that in the schema, and
b) write a resolve function that fetches the data
For example, you could have this schema:
type Query {
users(firstName: String!): [User]
}
type User {
firstName: String
lastName: String
}
You would have to define the following resolve function for the users field:
{
Query: {
users(root, args){
return sql.raw('SELECT * FROM `users` WHERE `firstName` LIKE ?', args.firstName);
}
}
}
And finally write this query to get a list of firstName and lastName of all the users that match your search criteria:
{
users(firstName: 'jason%'){
firstName
lastName
}
}
Here's a post I wrote a while ago that clarifies some of the concepts around GraphQL: https://medium.com/apollo-stack/how-do-i-graphql-2fcabfc94a01
And here's a post that explains the interplay between GraphQL schemas and resolve functions: https://medium.com/apollo-stack/graphql-explained-5844742f195e
Not sure if this is relevant to you because you want it to start with "jason" (ie would return "jason bourne" but not "bourne jason") but I recently came across a way to query GraphQL in a "%Like%" manner. For your use case it would look something like this:
export const allUsersQuery = `
query allUsers($UserName: String!){
allUsers(
filter: {first_name_contains: $UserName}
) {
id
first_name
...INSERT_OTHER_FIELDS_HERE...
}
}
`;
FWIW: I did this using a GraphCool BAAS. I don't think you were using GraphCool because GraphCool doesn't allow "_" in variable names.
Hope this helps someone down the line :)