chapter 5.2

Question 1

what are nested functions

Answer 1

it refers to functions being contained within another function

Question 2

how are nested functions evaluated

Answer 2

evaluation process begins from the innermost level to the outermost level

Question 3

what does the next_day() function do ?

Answer 3

The next_day function returns the first day of that month

Question 4

_________ is the value that is unavailable, unassigned, unknown or inapplicable

Answer 4

Null

Question 5

what are 4 different functions oracle has that pertain to the use of null values

Answer 5

NVL
NVL2
NULLIF
COALESCE

Question 6

what does the NVL function do

Answer 6

converts a null value to a known value of a fixed data type, either date, character, or number

Question 7

rule of NVL function

Answer 7

data types of null value column and the new value must be the same

Question 8

NVL synatax

Answer 8

NVL(column with null values, value to substitute for null)

Question 9

what happens when arithmetic calculation is performed with null

Answer 9

result is null

Question 10

nvl2 function evaluates the expression with ________ values

Answer 10

3

Question 11

how does NVL2 work

Answer 11

if the first values is not null, then the first expression is returned

if the first value is null, then the third expression is returned

Question 12

what are the data type restrictions in NVL2

Answer 12

values in expression 1 can have any data type

expression 2 and expression 3 can have any data type except LONG

Question 13

what is the data type returned in NVL2

Answer 13

The data type of the returned value is always the same as the data type of expression 2, unless expression 2 is character data, in which case the returned type is varchar2

Question 14

what does the NULLIF function do

Answer 14

compares 2 expressions and if they are equal, the function returns null
if they are not equal, the function returns the first expression

Question 15

what is the coalesce function is extension of _______

Answer 15

NVL function

Question 16

_____ means to come together

Answer 16

coalesce

Question 17

what does coalesce do ?

Answer 17

Coalesce(expression1, expression2, expression3, …)

Question 18

what does select coalesce(commission_pct, salary, 10) as “comm” return

Answer 18

if commission_pct is not null, it is returned
else it will check if salary has a value and return salary.

if commision_pct and salary are null it will return 10