Does Snowflake support primary keys or primary indexes?

Snowflake allows you to declare primary key constraints, but they are informational only; Snowflake does not enforce uniqueness or create an index on the column. The primary key is stored in the metadata and can be used by the query optimizer for certain optimizations, but it does not prevent duplicate rows. Snowflake also does not have traditional indexes. Instead, data is stored in micro‑partitions and automatically clustered. If you need to improve query performance on a column, you can define a clustering key, which reorganizes the micro‑partitions based on the key values.