Question

The table T(A, B, C, D) has a B-tree index on the column B. Which of the followine requests may benefit from the index? Where necessary, define additional conditions under which the index will be beneficial. If the query cannot benefit from the index, suggest other solutions for improving its performance. a. SELECT * FROM T WHERE B = x; b. SELECT * FROM T WHERE B <> x; c. SELECT * FROM T WHERE B LIKE 'x'; d. SELECT * FROM T WHERE SUBSTRING(B, 1, 1) 'x'

Answer 1

Answer:

Check the explanation

Explanation:

"Solutions (and any subsequent words) was ignored because we limit queries to 32 words."

The highest length in index key depends on the block size as well as the index storage parameters (the database of 75% block size minus some overhead). A B-tree index is limited to 32 columns.

Whenever the Oracle 11g is being utilized with all defaults in place (8k blocks), the highest index key length is 6398 bytes. Anything above this limit causes the error message “ORA-01450: maximum key length (6398) exceeded.”