Free 1Z0-883 Web TestEngine Demo

Q6 Single choice

Consider the query:
Mysql> SET @run = 15;
Mysql> EXPLAIN SELECT objective, stage, COUNT (stage) FROM iteminformation
WHERE run=@run AND objective='7.1' GROUP BY objective,stage
ORDER BY stage;

The iteminformation table has the following indexes;

Mysql> SHOW INDEXES FROM iteminformation:

This query is run several times in an application with different values in the WHERE clause in a growing data set.

What is the primary improvement that can be made for this scenario?

A
Execute the run_2 index because it has caused a conflict in the choice of key for this query.
B
Drop the run_2 index because it has caused a conflict in the choice of key for this query.
C
Do not pass a user variable in the WHERE clause because it limits the ability of the optimizer to use indexes.
D
Add an index on the objective column so that is can be used in both the WHERE and GROUP BY operations.
E
Add a composite index on (run,objective,stage) to allow the query to fully utilize an index.

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