Database users report that SELECT statements take a long time to return results. You run the following Transact-SQL statement
You need to create one nonclustered covering index that contains all of the columns in the above table. You must minimize index key size.
Which Transact-SQL statement should you run
A. CREATE NONCLUSTERED INDEX IX_User ON Users (CountryCode, UserName);
B. CREATE NONCLUSTERED INDEX IX_User ON Users (CountryCode, UserStatus) INCLUDE (UserName);
C. CREATE NONCLUSTERED INDEX IX_User ON Users (CountryCode, UserStatus, UserName);
D. CREATE NONCLUSTERED INDEX IX_User ON Users (UserStatus, CountryCode) INCLUDE (UserName);
B
equality columns should be put before the inequality columns, and together they should make the key of the index
https://docs.microsoft.com/en-us/sql/relational-databases/system-dynamic-management-views/sys-dm-db-missing-index-details-transact-sql?view=sql-server-ver15