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-- Oct 10 In-Class Exercise Thread

A →→ B is a MVD:
A B C
a b c
a x c
a b y
a x y

A →→ B isn't a MVD:
A B C
a b c
a x x
a b z
a x w

(Edited: 2018-10-15)

A →→ B is a MVD: A B C a b c a x c a b y a x y A →→ B isn't a MVD: A B C a b c a x x a b z a x w

-- Oct 10 In-Class Exercise Thread

MVD A->->B

A	B	C
a1	b1	c1
a1	b2	c2
a1	b1	c2
a1	b2	c1

Not an MVD:

A	B	C
a1	b1	c1
a1	b2	c2
a1	b3	c3
a1	b4	c4

MVD A->->B {| |- ! A !! B !! C |- | a1 || b1 || c1 |- | a1 || b2 || c2 |- | a1 || b1 || c2 |- | a1 || b2 || c1 |} Not an MVD: {| |- ! A !! B !! C |- | a1 || b1 || c1 |- | a1 || b2 || c2 |- | a1 || b3 || c3 |- | a1 || b4 || c4 |}

-- Oct 10 In-Class Exercise Thread

A B C

a b1 c1

a b2 c1

a b1 c2

a b2 c2

A -> -> B is a MVD

A B C

a b1 c1

a b2 c2

a b1 c3

a b2 c4

A -> -> B is not a MVD

(Edited: 2018-10-15)

A B C a b1 c1 a b2 c1 a b1 c2 a b2 c2 A -> -> B is a MVD A B C a b1 c1 a b2 c2 a b1 c3 a b2 c4 A -> -> B is not a MVD

-- Oct 10 In-Class Exercise Thread

Student: Conover Wang A | B | C

 a2 |  b2 |  c2
 a2 |  b2 | c3
 a2 |  b2 | c4
 a3 |  b3 | c3
 a3 |  b3 | c4

Not A -> -> B

  A | B |  C
 a2 |  b2 |  c2
 a2 |  b2 |  c3
 a2 |  b2 |  c4
 a3 |  b3 | c5
 a3 |  b3 | c6

Student: Conover Wang A | B | C a2 | b2 | c2 a2 | b2 | c3 a2 | b2 | c4 a3 | b3 | c3 a3 | b3 | c4 Not A -> -> B A | B | C a2 | b2 | c2 a2 | b2 | c3 a2 | b2 | c4 a3 | b3 | c5 a3 | b3 | c6

-- Oct 10 In-Class Exercise Thread

A - B - C 1 - 2 - 4 1 - 2 - 5 1 - 3 - 4 1 - 3 - 5 A ->-> B is an MVD

A - B - C 1 - 2 - 4 1 - 2 - 5 1 - 3 - 6 1 - 3 - 7 A ->-> B is not an MVD

A - B - C 1 - 2 - 4 1 - 2 - 5 1 - 3 - 4 1 - 3 - 5 A ->-> B is an MVD A - B - C 1 - 2 - 4 1 - 2 - 5 1 - 3 - 6 1 - 3 - 7 A ->-> B is not an MVD

-- Oct 10 In-Class Exercise Thread

A->->B is an MVD
|-------+------+-------|
| A | B | C |
|-------+------+-------|
| Bob | 1111 | Water |
| Bob | 1111 | Juice |
| Kelly | 2222 | Water |
| Kelly | 2222 | Juice |
|-------+------+-------|

A->->B is not an MVD
|-------+------+-------|
| A | B | C |
|-------+------+-------|
| Bob | 1111 | Water |
| Bob | 1111 | Juice |
| Kelly | 2222 | Milk |
| Kelly | 3333 | Soda |
|-------+------+-------|

(Edited: 2018-11-07)

A->->B is an MVD |-------+------+-------| | A | B | C | |-------+------+-------| | Bob | 1111 | Water | | Bob | 1111 | Juice | | Kelly | 2222 | Water | | Kelly | 2222 | Juice | |-------+------+-------| A->->B is not an MVD |-------+------+-------| | A | B | C | |-------+------+-------| | Bob | 1111 | Water | | Bob | 1111 | Juice | | Kelly | 2222 | Milk | | Kelly | 3333 | Soda | |-------+------+-------|

-- Oct 10 In-Class Exercise Thread

A | B | C

x y m

x z n

x y n

x z m

A ->>B is an MVD because for each value of x there is more than one value of B as well as B and C are independent. This table is bad design because it could be split up into two tables instead.

A | B | C

x y m

x z n

x y o

x z p

A ->> B is not an MVD

(Edited: 2018-11-19)

A | B | C x y m x z n x y n x z m A ->>B is an MVD because for each value of x there is more than one value of B as well as B and C are independent. This table is bad design because it could be split up into two tables instead. A | B | C x y m x z n x y o x z p A ->> B is not an MVD