Constraints define integrity and consistency rules for data stored in tables. Snowflake provides support for constraints as defined in the ANSI SQL standard, as well as some extensions for compatibility with other databases, such as Oracle.
Snowflake supports defining and maintaining constraints, but does not enforce them, except for NOT NULL constraints, which are always enforced.
Constraints are provided primarily for data modeling purposes and compatibility with other databases, as well as to support client tools that utilize constraints. For example, Tableau supports using constraints to perform join culling (join elimination), which can improve the performance of generated queries and cube refresh.