What's the difference between a user-defined schema and a shared schema in Snowflake?
In Snowflake, both user-defined schemas and shared schemas are used to organize and manage database objects, but they serve different purposes and have distinct characteristics:
**User-Defined Schema:**
1. **Ownership:** User-defined schemas are owned by a specific user or role. The owner has full control over the schema and can grant privileges to other users and roles.
2. **Access Control:** The owner of a user-defined schema can control access to the schema and its objects by granting or revoking privileges to other users and roles.
3. **Data Segregation:** User-defined schemas are often used to segregate data and objects based on projects, teams, applications, or any other criteria. Each user or role can have their own set of schemas to manage their objects.
4. **Default Schema:** Users and roles can have a default schema set, which determines the schema where new objects are created by default.
**Shared Schema:**
1. **Ownership:** Shared schemas are typically owned by a system-defined role such as **`PUBLIC`** or a specific role designated for shared access. They are not owned by individual users or roles.
2. **Access Control:** Access to shared schemas is controlled by Snowflake administrators. They grant necessary privileges to roles or users that need to interact with the shared schema.
3. **Centralized Data:** Shared schemas are often used for centralizing data that needs to be accessed by multiple users or teams. They provide a common location for shared data assets.
4. **Data Collaboration:** Shared schemas facilitate collaboration by providing a standardized location for shared objects and data. Different teams or users can access and use the same data assets.
5. **Default Schema:** Shared schemas are not typically set as default schemas for users or roles since they are intended to be shared among multiple entities.
In summary, user-defined schemas are used to organize and manage data and objects for specific users or roles, allowing for data segregation and customized access control. Shared schemas, on the other hand, are used for centralized and shared data assets that need to be accessed by multiple users or teams. Snowflake administrators control access to shared schemas, while the owner of a user-defined schema has more control over its management.
