Using Null Quiz

Test your understanding of the NULL value

teacher

id	dept	name	phone
101	1	Shrivell	2753
102	1	Throd	2754
103	1	Splint
104		Spiregrain
105	2	Cutflower	3212
106		Deadyawn

dept

id	name
1	Computing
2	Design
3	Engineering

Select the code which uses an outer join correctly.

 SELECT teacher.name, dept.name FROM teacher JOIN dept ON (dept = id)

 SELECT teacher.name, dept.name FROM teacher, dept INNER JOIN ON (teacher.dept = dept.id)

 SELECT teacher.name, dept.name FROM teacher, dept JOIN WHERE(teacher.dept = dept.id)

 SELECT teacher.name, dept.name FROM teacher OUTER JOIN dept ON dept.id

 SELECT teacher.name, dept.name FROM teacher LEFT OUTER JOIN dept ON (teacher.dept = dept.id)

Select the correct statement that shows the name of department which employs Cutflower -

 SELECT dept.name FROM teacher JOIN dept ON (dept.id = (SELECT dept FROM teacher WHERE name = 'Cutflower'))

 SELECT dept.name FROM teacher JOIN dept ON (dept.id = teacher.dept) WHERE dept.id = (SELECT dept FROM teacher HAVING name = 'Cutflower')

 SELECT dept.name FROM teacher JOIN dept ON (dept.id = teacher.dept) WHERE teacher.name = 'Cutflower'

 SELECT dept.name FROM teacher JOIN dept WHERE dept.id = (SELECT dept FROM teacher WHERE name = 'Cutflower')

 SELECT name FROM teacher JOIN dept ON (id = dept) WHERE id = (SELECT dept FROM teacher WHERE name = 'Cutflower')

Select out of following the code which uses a JOIN to show a list of all the departments and number of employed teachers

 SELECT dept.name, COUNT(*) FROM teacher LEFT JOIN dept ON dept.id = teacher.dept

 SELECT dept.name, COUNT(teacher.name) FROM teacher, dept JOIN ON dept.id = teacher.dept GROUP BY dept.name

 SELECT dept.name, COUNT(teacher.name) FROM teacher JOIN dept ON dept.id = teacher.dept GROUP BY dept.name

 SELECT dept.name, COUNT(teacher.name) FROM teacher LEFT OUTER JOIN dept ON dept.id = teacher.dept GROUP BY dept.name

 SELECT dept.name, COUNT(teacher.name) FROM teacher RIGHT JOIN dept ON dept.id = teacher.dept GROUP BY dept.name

Using SELECT name, dept, COALESCE(dept, 0) AS result FROM teacher on teacher table will:

display 0 in result column for all teachers

display 0 in result column for all teachers without department

do nothing - the statement is incorrect

set dept value of all teachers to 0

set dept value of all teachers without department to 0

Query:

SELECT name,
       CASE WHEN phone = 2752 THEN 'two'
            WHEN phone = 2753 THEN 'three'
            WHEN phone = 2754 THEN 'four'
            END AS digit
  FROM teacher

shows following 'digit':

'four' for Throd

NULL for all teachers

NULL for Shrivell

'two' for Cutflower

'two' for Deadyawn

Select the result that would be obtained from the following code:

 SELECT name, 
      CASE 
       WHEN dept 
        IN (1) 
        THEN 'Computing' 
       ELSE 'Other' 
      END 
  FROM teacher

Table-A

Shrivell	Computing
Throd	Computing
Splint	Computing
Spiregrain	Other
Cutflower	Other
Deadyawn	Other

Table-B

Shrivell	Computing
Throd	Computing
Splint	Computing
Spiregrain	Computing
Cutflower	Computing
Deadyawn	Computing

Table-C

Shrivell	Computing
Throd	Computing
Splint	Computing

Table-D

Spiregrain	Other
Cutflower	Other
Deadyawn	Other

Table-E

Shrivell	1
Throd	1
Splint	1
Spiregrain	0
Cutflower	0
Deadyawn	0