Materialized views provide a persisted snapshot of data, differentiating them from Regular views.

Data Vault provides the historical tracking and auditability needed, while point-in-time tables on top optimize for BI queries. Snowflake schema with SCD2 also allows historical tracking within a dimensional model. SCDI alone will not preserve history, and SCDO locks in attributes indefinitely. A wide denormalized table is not suitable for historical analysis or frequent updates and can lead to redundancy. Therefore options B and C are suitable for BI reporting.

Creating 'SALES LAST 30 DAYS' table and joining is the most effective strategy because it reduces the size of the SALES table significantly before the join operation. Materialized views (A) are generally effective, but the high update frequency of the SALES table could lead to significant overhead in materialized view maintenance. Standard indexes (B) are not supported in Snowflake. Search optimization (C) may not be suitable as the could have high cardinality. Clustering (D) could improve performance, but the benefits might not outweigh the cost of reclustering after frequent data loading, and it does not limit the initial size of the join.

Connecting BI tools to Snowflake enables seamless integration and data visualization in dashboard creation.

Option C is the correct answer. It first uses 'REGEXP REPLACE(phone_number, '[AO-91+', to remove all non-numeric characters from the phone number. Then, it uses a 'CASE statement to check if the resulting string has a length of 10 (a valid phone number length after standardization). If it does, the standardized phone number is returned; otherwise, NULL is returned. Option A only removes non-numeric characters but doesn't handle invalid lengths. Option B and D is doing same ,using 'IFF and adds unnecessary complexity by using 'IS NUMERIC' which is redundant since 'REGEXP REPLACE ensures only numbers exist. Option E filters on 'WHERE' Clause that reduces the record which are having length of 10, But Question needs to return NULL for invalid entries .