A、A primary key must exist for creation of a clustered index

B、A clustered index allows fulltext searching within InnoDB

C、The first unique index is always used as a clustered index and not a primary key

D、A clustered index provides direct access to a page containing row data

E、If no indexes exist, a hidden clustered index is generated based on row IDs

F、A primary key is used as a clustered index

G、A clustered index is a grouping of indexes from different tables into a global index for faster searching