10/9 Class

Question 1

difference between datawarehouse and database

Answer 1

the way the data is organized

Question 2

step 1

Answer 2

decide on the data format:
data type
length
null or not null

Question 3

char(size)

Answer 3

size is the number of characteristics to store

Question 4

varchar(size)

Answer 4

size is the number of characters to store, between variable length string

Question 5

integer

Answer 5

stores ranges of integer values

Question 6

decimal(p,s)

Answer 6

P is the precision and s is the scale

ex: deimal (7,2) is a number that has 5 digits before the decimal and 2 digits after the decimal

Question 7

Step 2

Answer 7

decide index attributes

Question 8

date time

Answer 8

stores year, month, day, hours, minutes, and seconds

Question 9

disk

Answer 9

is the slowest part of our index

Question 10

logical unit of transfer data(block)

Answer 10

4k bytes, 0.01 seconds

Question 11

index table

Answer 11

only has two attributes

key: unique key, pointer: shows which block it is in

Question 12

B+ tree index

Answer 12

where there are multiple indexes in our records

Question 13

height of the tree

Answer 13

log2n the two is based on a two block table

Question 14

time process structure

Answer 14

4min non index
12s simple index
.21 s b+ tree

Question 15

oracle command for creating B+tree index

Answer 15

create index pidindex ON product(product_key)

Question 16

bitmap index

Answer 16

collection of bit vectors, one for each possible value of A. The vector for value v has 1 in position i if the ith record has v
more common in data warehouse

Question 17

aggregation

Answer 17

can be an alternative or a complement to indexes on tables

Question 18

data cleaning(missing values)

Answer 18

1. exclude the record
2. exclude the attribute/field
3. replaced by a global constant
4. replaced by the attribute mean
   5 Replaced by the most probable value
   6 Manual correction
   7 Apply specific algorithm

Question 19

imputation

Answer 19

used to find a missing value, it uses regression

Question 20

data integration common challenges

Answer 20

same attribute with different name

different attribute with same name

Question 21

data integration process

Answer 21

1. Get source and target schemas
2. Integrate source schema and map to data warehouse schema with the help from: business domain experts, source system tech experts, ETL tools

Question 22

maintenance

Answer 22

DW refreshment, is the process of keeping data in DW consistent/current with data in source systems