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Question ID 2500

Which three statements are true about histograms?
 

Option A

A.    They capture the distribution of different values in an index for better selectivity estimates.
 

Option B

B.    They can be used only with indexed columns.
 
 

Option C

C.    They provide metadata about distribution of and occurrences of values in a table column.
 

Option D

D.    They provide improved selectivity estimates in the presence of data skew, resulting in execution plans with uniform distribution.
 

Option E

E.    They help the optimizer in deciding whether to use an index or a full table scan.

 

Option F

F.    They help the optimizer to determine the fastest table join order.

Correct Answer C,E,F
Description Update Date and Time 2016-01-09 17:04:36

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Question ID 2501

View the exhibit and examine the query and its execution plan from the PLAN_TABLE. Which statement is true about the execution?

Option A

A.    The row with the ID column having the value 0 is the first step execution plan.
 

Option B

B.    Rows are fetched from the indexes on the PRODUCTS table and from the SALES table using full table scan simultaneously, and then hashed into memory.
 

Option C

C.    Rows are fetched from the SALES table, and then a hash join operator joins with rows fetched from indexes on the PRODUCTS table.

 

Option D

D.    All the partitions of the SALES table are read in parallel.

Correct Answer C
Description Update Date and Time 2016-01-09 17:06:37

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