Question 1

What is GraphQL SDL?

Accepted Answer

GraphQL SDL (Schema Definition Language) is the declarative syntax used to define a GraphQL API's types, queries, mutations, and subscriptions. It is human-readable and framework-agnostic.

Question 2

What are the main types in GraphQL SDL?

Accepted Answer

The main types are: type (object types), input (input objects for mutations), enum (enumeration types), interface (abstract types), union (multiple possible types), and scalar (custom scalar types).

Question 3

What is the difference between Query and Mutation in GraphQL?

Accepted Answer

Query is for read operations that don't change data. Mutation is for write operations that create, update, or delete data. Both are defined as fields on their respective type in the schema.

Question 4

What does ! mean in GraphQL types?

Accepted Answer

The ! (exclamation mark) after a type means the field is non-null and always returns a value. Without !, the field can return null. [String!]! means a non-null array of non-null strings.

Question 5

How do I validate a GraphQL schema?

Accepted Answer

Use graphql-js's buildSchema() or parse() functions to validate SDL syntax. Tools like Apollo Studio and GraphQL Playground provide real-time schema validation and exploration.

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