50 lines
890 B
Markdown
50 lines
890 B
Markdown
|
---
|
||
|
|
categories:
|
||
|
|
- Databases
|
||
|
|
tags: [graph-ql]
|
||
|
|
---
|
||
|
|
|
||
|
|
# Schema Definition Language
|
||
|
|
|
||
|
|
SDL is the formal name for the syntax of GraphQL schemas.
|
||
|
|
|
||
|
|
A schema is a collection of object types that contain fields. Each field has a type of its own. A field's type can be a primitive/scalar value (such as an Int or a String), or it can be another object type (just like a custom type in TS).
|
||
|
|
|
||
|
|
A schema's type can be non-nullable which is to say, a required field. We indicate this with `!`.
|
||
|
|
|
||
|
|
A type for a field can be a collection/array of a given type.
|
||
|
|
|
||
|
|
The following example indicates these properties:
|
||
|
|
|
||
|
|
```gql
|
||
|
|
type Person {
|
||
|
|
age: Int
|
||
|
|
name: String
|
||
|
|
pets: [Pet]!
|
||
|
|
}
|
||
|
|
|
||
|
|
type Pet {
|
||
|
|
species: String
|
||
|
|
name: String
|
||
|
|
age: Int
|
||
|
|
}
|
||
|
|
```
|
||
|
|
|
||
|
|
## Descriptions
|
||
|
|
|
||
|
|
Descriptions are comments that allow you to document your Schema
|
||
|
|
|
||
|
|
Single line:
|
||
|
|
|
||
|
|
```gql
|
||
|
|
"Single line comment"
|
||
|
|
```
|
||
|
|
|
||
|
|
```gql
|
||
|
|
"""
|
||
|
|
Multi
|
||
|
|
line
|
||
|
|
comment
|
||
|
|
"""
|
||
|
|
```
|