19. Which of the following are valid Optimizer directives? (Choose all that appl
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Question
19. Which of the following are valid Optimizer directives? (Choose all that apply) *This question is required.
a. EXPLAIN
b. MULTI_INDEX
c. INDEX_ALL
d. AVOID_MULTI_INDEX
20. An error was generated when the following SQL statement was executed:
ALTER TABLE tab1 MODIFY col1 DATE CHECK (col1 > col2) CONSTRAINT my_constraint;
Why was the error generated? *This question is required.
a. Because you cannot use an ALTER TABLE … MODIFY .. to add a constraint to a column
b. Because a CHECK constraint on a column can only reference that column
c. Because a CHECK constraint cannot be added to an existing column
d. Because a CHECK constraint cannot be added to a DATE column
21. Which of the following statements are TRUE concerning Optimizer directives? (Choose all that apply) *This question is required.
a. Optimizer directives can be used in SELECT statements
b. Optimizer directives cannot be used in UPDATE and DELETE statements
c. Optimizer directives cannot be used in views, stored procedures, or triggers
d. Multiple optimizer directives can be used on the same SQL statement
22. Non-logging databases use which isolation level? *This question is required.
a. Dirty Read
b. Committed Read
c. Cursor Stability
d. Repeatable Read
Explanation / Answer
19. Which of the following are valid Optimizer directives? (Choose all that apply) *This question is required.
a. EXPLAIN
b. MULTI_INDEX
c. INDEX_ALL
d. AVOID_MULTI_INDEX
ANSWER: OPTION B,C,D are valid optimizers..Explain is not an optimizer
20. An error was generated when the following SQL statement was executed:
ALTER TABLE tab1 MODIFY col1 DATE CHECK (col1 > col2) CONSTRAINT my_constraint;
Why was the error generated? *This question is required.
a. Because you cannot use an ALTER TABLE … MODIFY .. to add a constraint to a column
b. Because a CHECK constraint on a column can only reference that column
c. Because a CHECK constraint cannot be added to an existing column
d. Because a CHECK constraint cannot be added to a DATE column
ANSWER: OPTION (D).The error generated is option D
EXPLANATION:
21. Which of the following statements are TRUE concerning Optimizer directives? (Choose all that apply) *This question is required.
a. Optimizer directives can be used in SELECT statements
b. Optimizer directives cannot be used in UPDATE and DELETE statements
c. Optimizer directives cannot be used in views, stored procedures, or triggers
d. Multiple optimizer directives can be used on the same SQL statement
ANSWER: OPTION (A,D) is true
EXPLANATION:Optimizer Directives can be used for SQL select statement
22. Non-logging databases use which isolation level? *This question is required.
a. Dirty Read
b. Committed Read
c. Cursor Stability
d. Repeatable Read
ANSWER: OPTION (C)
EXPLANATION:Cursor Stability has the lock option in which it can terminate with out displaying log database
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