chapter 2

Question 1

why can the describe command be abbreviated

Answer 1

In general, SQL keywords cannot be abbreviated. DESCRIBE is an Oracle Proprietary command, which is
why it can be abbreviated to DESC.

Question 2

what does the desc cmd return

Answer 2

table name
data types
primary keys
foreign keys
nullable columns
length
precision
scale

Question 3

what is concatenation

Answer 3

it means to connect or link together in a series

Question 4

symbol for concatenation

Answer 4

||
double pipe character

Question 5

when values are concatenated the result is a __________

Answer 5

character string

Question 6

what happens when you don’t use a column alias when doing a concatenation operation

Answer 6

column aliases are useful when performing concatenation so that the default select line does not appear as the column heading

Question 7

what is a literal value

Answer 7

it is a fixed data value such as a character, number or date

Question 8

True or False
Number literals do not have to be enclosed in single quotes

Answer 8

True

Question 9

what command will you use to find out how many unique instances of something exist

Answer 9

DISTINCT COMMAND

Question 10

what is the syntax for distinct

Answer 10

select distinct <column_name> from <table_name>;</table_name></column_name>

Question 11

Where in the query does the distinct command appear

Answer 11

Must appear directly after the select keyword

Question 12

______ is optional in a select statement

Answer 12

Where clause

Question 13

______- cannot be used in where clause

Answer 13

Alias

Question 14

what are the comparison operators for not equal to

Answer 14

^=

!=

<>

Question 15

character strings and dates in the where clause must be enclosed in ______

Answer 15

single quotation marks ‘ ‘

Question 16

all character searches in the where clause are _____

Answer 16

case - sensitive

Question 17

What are the acceptable formats for date values

Answer 17

–> dash
–> forward slash
they can be in either upper, lower or initcap format

also remember to use 4 digit year values

Question 18

what is the between …and operator used for

Answer 18

it is used to select and display rows based on a range of values which are inclusive of the specified lower and upper limits

Question 19

_____ value must be listed first in the between … and operator

Answer 19

lower limit

Question 20

is there a performance benefit/drawback in using >= and <= over between …and operator ?

Answer 20

No, between …and is used over >= and <= as it is simpler to read

Question 21

the ‘in’ condition is also known as ?

Answer 21

membership condition

Question 22

what is the in condition used for

Answer 22

it is used to test whether a value is IN a specified set of values

Question 23

what is the LIKE condition in sql

Answer 23

allows you to select rows that match either characters, dates, or number patterns

Question 24

what are 2 wildcard characters in sql

Answer 24

% and _ (underscore)

Question 25

what are the wildcard characters used for in sql

Answer 25

used to construct a search string

Question 26

what is the % symbol used to represent

Answer 26

used to represent any sequence of ZERO or more characters

Question 27

what is _ symbol used to represent

Answer 27

used to represent a single character

Question 28

WHERE last_name LIKE '_o%' represent

Answer 28

shows all the last names which have the second letter as o

Question 29

What is an escape option

Answer 29

--> is it used to indicate that the _ or % is part of the name, not a wildcard value --> any character can be used as the escape character

Question 30

what is the syntax for escape character

Answer 30

SELECT last_name, job_id FROM employees WHERE job_id LIKE '%\_R' ESCAPE ' \ '

Question 31

which condition tests for data that is available in the database

Answer 31

IS NOT NULL

Question 32

which condition tests for data that is unavailable, unassigned or unknown data

Answer 32

IS NULL

Question 33

why does the column = NULL not work

Answer 33

This query will run, but it will not return any data, as the actual value of NULL is unknown.