23. You want to set the isolation mode of your transaction to CURSOR STABILITY.
ID: 3594715 • Letter: 2
Question
23. You want to set the isolation mode of your transaction to CURSOR STABILITY. Which of the following statements will do this? (Choose all that apply) *This question is required.
a. SET TRANSACTION ISOLATION LEVEL CURSOR STABILITY
b. SET ISOLATION TO CURSOR STABILITY
c. SET CURSOR STABILITY
d. CURSOR STABILITY ON
24. For a particular query, the Informix Optimizer chooses an Index access path, as shown below:
Index Name: user1.my_idx_tab1
Index Keys: col1 col2 col3 (Key-Only) (Serial, fragments: ALL)
Lower Index Filter: user1.tab1.col1 > 350
Upper Index Filter: user1.tab1.col1 < 750
Based on an analysis of this information, which of the following statements must be TRUE? (Choose all that apply) *This question is required.
a. The statement that was explained included a table named tab1
b. There is an index named my_idx_tab1 which indexes the columns col1, col2, and col3, in that order
c. The statement that was explained had a WHERE clause which included the following: col1 > 350 AND col1 < 750
d. When executing the query, the system only needs to read an index, and does not need to access the rows in a table
25. You execute the following statements:
SET EXPLAIN ON;
SELECT * FROM TAB1 WHERE COL1 = 100;
SELECT * FROM TAB2 WHERE COL2 = 120 and COL1 < 100;
SET EXPLAIN OFF;
The EXPLAIN output shows that the first SELECT has an estimated cost of 20 and the second SELECT has an estimated cost of 10. What can you say about the relative costs of the two queries? *This question is required.
a. The first SELECT will take twice as long to execute as the second SELECT
b. The first SELECT will use twice as many resources as the second SELECT
c. The first SELECT will return twice as many rows as the second SELECT
d. The costs of the two SELECT statements cannot be directly compared
26. Which of the following join methods can be selected by the Informix Optimizer? (Choose all that apply) *This question is required.
a. Nested Loop
b. Merge
c. Hash
d. Hybrid
Explanation / Answer
[23] [A]
Explaination :
SET [GLOBAL | SESSION] TRANSACTION
transaction_property [, transaction_property] ...
transaction_property:
ISOLATION LEVEL level
| READ WRITE
| READ ONLY
level:
REPEATABLE READ
| READ COMMITTED
| READ UNCOMMITTED
| SERIALIZABLE
[24] [B] There is an index named my_idx_tab1 which indexes the columns col1, col2, and col3, in that order.
[25] [B]
COST : The value of this column does not have any particular unit of measurement, it is merely a weighted value used to compare costs of execution plans.
[26] [A] Nested loop Join
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.