How do relational databases work mathematically?

Answers

Answer 1

Answer:

A relational database stores data in a series of tables so that the data models a mathematical theory of relations. The model allows for queries based on projection, selection, and join, among other operations, and connects the data in the tables by way of keys.

Answer 2

Answer:

Well, I guess in a formal sense you could call relational algebra a type of logic, which puts it into the realm of ‘math’, though I don’t think most mathematicians would look at it as being a very significant area, more ‘applied logic’ than anything else.

That being said, relational algebra DOES present some formalisms in the shape of relations, tuples, normalizations, and denormalization, etc. There is also a model of sequential operations and thus the underpinnings of the ACID database concept.

Since the overwhelming primary use of RA has been as a way to structure our ideas about SQL RDBMSes there isn’t really a lot of deep theory there. I don’t think anyone has really built any other models of RA beyond an RDBMS. There have been limited non-SQL RDBMS implementations, but AFAIK none of them are really actively maintained today.


Related Questions

The velocity of a car over five hours is given by v(t) = 60 ln(t + 1), 0 < t < 5
in kilometers per hour. What is the total distance traveled from t = 0 to t = 5?
Round your answer to the nearest whole number and do not include units.

Answers

Answer:

345

Step-by-step explanation:

The velocity of a car over five hours is given by:

[tex]\displaystyle v(t)=60\ln(t+1),\, 0 \leq t \leq 5[/tex]

And we want to find the total distance traveled from t = 0 to t = 5.

Recall that distance is the integral of the absolute value of the velocity function. Since we want to find the total distance traveled from t = 0 to t = 5, our limits of integration are t = 0 and t = 5. Hence:

[tex]\displaystyle D=\int_0^5 |\underbrace{60\ln(t+1)}_{v(t)}|\, dt[/tex]

Since v(t) ≥ 0 for all t in the interval [1, 5], we can remove the absolute value. Use a calculator:

[tex]\displaystyle D=60\left(6\ln(6)-5)=345.0334...\approx 345[/tex]

solve for x. Round to the nearest tenth, if necessary.​

Answers

Answer:

50.8°

Step-by-step explanation:

In ∆ IJK :-

sin x = 6.2/8 x = sin -¹ ( 62/80) x = sin -¹ ( 31/40 ) x = 50.8°

Please help me with this

Answers

Answer:

52 in^2

Hope this helps!

How many terms are in the algebraic expression

Also, What do they mean by "Terms"

Answers

Answer:

There are 4 terms

Step-by-step explanation:

A term is a single mathematical expression. Terms can be identified with a plus or minus sign in front of them. Terms can also be multiplied and divided.

So, in this case, the terms are:

-7

12x^4

-5y^8

x

Which of the Following best describes a cylinder?

Answers

Answer:

D

Step-by-step explanation:

all the options seems similar..but i can find the D more suitable

Can someone help me with this math homework please!

Answers

Answer:

The first answer

Step-by-step explanation:

Domain refers to the set of x values and range refers to the set of y values. Since x goes from 0 to 3, and does not exclude any values within those numbers, the first answer applies to that set.

Answer:

option 1

that is

{t| 0 <= t <= 3}

Step-by-step explanation:

as the graph plots height ove time

time will be the domain, taken on the x axis, with values ranging from 0 to 3.

so the domain is

{t| 0 <= t <= 3}

if u help me i will give you brainliest <3

Answers

Answer:

a) 6

b) 12:35 ( not so sure about this one)

Step-by-step explanation:

a)

distance = speed * time

ruths distance = 4* 1.5 (because it takes her 1h 30 mins)

distance = 6miles    

b)  1/4 here is quarter so, 15mins

10:30 and then add 50 mins to that.

     she leaves at 11:20 and takes 1h and 15 mins ( 75mins) to walk home

     so 11:20 + 1h 15min

     = 12:35

hope this helps :)

Answer:

a) 6 miles

b) 12:35 pm

Step-by-step explanation:

a) 9 am to 10:30 am = 1 hour and 30 mins = 1.5 hours

4mph x 1.5 = 6miles

b) 10:30 am + 50 mins = 11:20 am

1 hour = 60 mins

60/4 = 15 mins

1 1/4 = 1 hour 15 mins

11:20 am + 1 hour 15 mins = 12:35 pm

Choose the smallest number 3 1/8 or 10/3

Answers

Answer:

10/3

Step-by-step explanation:

31/8= 3.8

10/3= 3.3

A basketball-player scores a free-throw with probability 0.9. What is the probability that her first miss occurs on the 6th shot

Answers

Answer:

[tex]Pr = 0.059049[/tex]

Step-by-step explanation:

Given

[tex]p = 0.9[/tex] --- probability of scoring

Required

Probability that his first miss is his 6th shot

Let q represent the event that he did not score.

Using complement rule:

[tex]q = 1 - p = 1 - 0.9 = 0.1[/tex]

The event that his first miss is his 6th is represented as:

p p p p p q ---- That he scoress the first 5 attempts

So, the probability is:

[tex]Pr = p^5 * q[/tex]

[tex]Pr = 0.9^5 * 0.1[/tex]

[tex]Pr = 0.059049[/tex]

D=rt What does T equal? Lol how is this possible

Answers

Answer:

t = D/r

Step-by-step explanation:

you rearrange the equation so that is the subject. when you bring something over the equal sign, it reverses the function so D = r×t becomes t = D/r

Ethan buys 4 pack of muffins. he uses a coupon an saves 2$ off total.

Which expression represents his total cost?

Answers

Answer:

4x-2

Step-by-step explanation:

X=muffins

At Billy's school, 80 students come to school by bicycle or by car. Together, the vehicles they arrive to school in have 270 wheels. How many of each are used

Answers

Answer:

x = number of bicycles = 35

y = number of cars = 55

Step-by-step explanation:

Let

x = number of bicycles

y = number of cars

x + y = 80 (1)

2x + 4y = 270 (2)

From (1)

x = 80 - y

Substitute x = 80 - y into (2)

2x + 4y = 270 (2)

2(80 - y) + 4y = 270

160 - 2y + 4y = 270

- 2y + 4y = 270 - 160

2y = 110

y = 110/2

y = 55

Substitute y = 55 into (1)

x + y = 80 (1)

x + 55 = 80

x = 80 - 55

x = 35

x = number of bicycles = 35

y = number of cars = 55

Which inequality describes the graph?

Answers

Answer:

1 describe the inequality graph

Find the length of the line AB if A is (-2,3) and B is (5,7)

Answers

Answer:

[tex]{ \tt{length = \sqrt{ {( - 2 - 5)}^{2} + {(3 - 7)}^{2} } }} \\ = \sqrt{65} \\ = 8.06 \: units[/tex]

HELP. Drag the tiles to the correct boxes to complete the pairs.
Match each product of complex numbers with its value.

Answers

Answer:

[tex]i^{2} (2i^{2} -5)[/tex]

[tex]2i^{2} \times i^{2} -5i^{2}[/tex]

[tex]2(-1)(-1)-5(-1)[/tex]

[tex]2+5[/tex]

[tex]=7[/tex]  [tex]i^{2}(2i-5)[/tex]

------------------

[tex]i^{2} (3+i^{2} )[/tex]

[tex]i^{2} \times 3+i^{2} \times i^{2}[/tex]

[tex](-1)3+(-1)(-1)[/tex]

[tex]-3+1[/tex]

[tex]-2[/tex]  [tex]=i^{2} (3+i^{2} )[/tex]

---------------------

[tex]2i(2i-i^{3} )[/tex]

[tex]2i\times 2i-i^{3} \times2i[/tex]

[tex]4i^{2} -2i^{4}[/tex]

[tex]4(-1)-2(1)[/tex]

[tex]-4-2=[/tex]

[tex]-6=2i(2i-i^{3} )[/tex]

-------------------

[tex]i(4i^{3} -i)[/tex]

[tex]4i^{3} \times i-i\times i[/tex]

[tex]4i^{4} -i^{2}[/tex]

[tex]4(1)-(1)[/tex]

[tex]4+1=5[/tex]

--------------------

ANSWER:

[tex]-6\Longrightarrow 2i(2i-i^{3} )[/tex]

[tex]5\Longrightarrow i(4i^{3} -i)[/tex]

[tex]7\Longrightarrow i^{2} (2i-5)[/tex]

[tex]-2\Longrightarrow i^{2} (3+i^{2} )[/tex]

----------------------------

Hope it helps...

Have a great day!!

subtract the following rational expressions
[tex] \frac{8k}{9k - 4} - \frac{3k^3}{2k + 7} [/tex]
please show all work​

Answers

Answer:

-27k^4 +12k^3+16k^2+56k

---------------------

(9k-4)(2k+7)      

Step-by-step explanation:

8k                  3k^3

---------   -  -----------

9k-4             2k+7

Get a common denominator

8k *(2k+7)          3k^3 *(9k-4)

---------      -           -----------

(9k-4)(2k+7)        (9k-4)(2k+7)

Combine

8k *(2k+7) -3k^3 *(9k-4)

---------------------

(9k-4)(2k+7)        

Distribute

16k^2+56k -27k^4 +12k^3

---------------------

(9k-4)(2k+7)      

-27k^4 +12k^3+16k^2+56k

---------------------

(9k-4)(2k+7)        

Type your response in the box. Imagine that this graph represents the distance Brianna travels to get to her babysitting job with respect to time. Describe a relation that the graph may represent.

Answers

Answer:

Brianna left home and drove 3 miles in 6 minutes. She then stopped for 4 minutes to pick up coffee. Finally, she traveled the last 4 miles in 6 minutes to arrive at her babysitting job.

Step-by-step explanation:

This answer is from Plato.

The gradient of the line passing through A (2,3), B (k,7) is
23
23

. Find the value of k. help pls

Answers

Given:

The gradient of the line passing through A(2,3), B(k,7) is [tex]\dfrac{2}{3}[/tex].

To find:

The value of k.

Solution:

The gradient or slope of a line is:

[tex]m=\dfrac{y_2-y_1}{x_2-x_1}[/tex]

The gradient of the line passing through A(2,3), B(k,7) is [tex]\dfrac{2}{3}[/tex]. So,

[tex]\dfrac{2}{3}=\dfrac{7-3}{k-2}[/tex]

[tex]\dfrac{2}{3}=\dfrac{4}{k-2}[/tex]

On cross multiplication, we get

[tex]2(k-2)=4(3)[/tex]

[tex]2k-4=12[/tex]

[tex]2k=12+4[/tex]

[tex]2k=16[/tex]

Divide both sides by 2.

[tex]k=\dfrac{16}{2}[/tex]

[tex]k=8[/tex]

Therefore, the value of k is 8.

A bag contains 13 blue marbles, 12 red marbles, 6 yellow marbles, and 8 green marbles. What is the probability of picking a red marble, putting that one back and then picking another red marble?

Answers

Answer:

(12/39) * (12/39) or 16/169

Step-by-step explanation:

Uma empresa do ramo de confecções produz e comercializa calças jeans. Se x representa a quantidade produzida e comercializada (em milhares de reais) e L(x) = -x² + 8x – 16 representa o lucro (em milhares de reais) da empresa para x unidades, então quando L(x) = 0 a empresa terá produzido e comercializadas quantas unidades dessas calças jeans? *

Answers

Answer:

I am in 5 classso i did not known answer

What are the steps in order of operations

Answers

Answer:

PEMDAS

Step-by-step explanation:

PEMDAS best identifies all of the steps in order of operation

where PEMDAS stands for parentheses exponents multiplication division addition and subtraction

Hope this helps!
PEMDAS .

P = Parentheses ( )
E = Exponents 2^2
M = Multiplication x
D = Division /
A = Addition +
S = Subtraction -

Find the height h of the triangle.

Answers

Answer:

A, 12 times the square root of 3

Step-by-step explanation:

24 sqaured plus 12 squared=432

square root of 432=20.9

12 times the sqaure root of 3=20.9

7. The revenue for the school play is given by: R= -50t^2 + 300t , where “t” is the ticket price in dollars. The cost to produce the play is given by: C = 600-50t. Determine the ticket price that will allow the school play to break even. (Note: breaking even means that revenue = cost.) Sketch the graphs of both equations as seen on your calculator (indicate the window you used
in the space provided).

Answers

Answer:

R= -50t^2 + 300t

-50tt(t-6)

-50(t-12)

so lets say that they sold 10 dollar tickets

-5000(4)

so they would lose -20000 dollars

-50(-2)

and the play would cost 100 dollars

Hope This Helps!!!

A rectangle has a perimeter of 80 cm and its length is 1 cm more than twice its width. Find the dimensions of a rectangle given that its perimeter is 80 cm and its length is 1 cm more than twice its width. Set up your solution using the variables L for the length, W for the width, and P for the perimeter. Part a: Using the definition of the perimeter, write an equation for P in terms of L and W. Part b: Using the relationship given in the problem statement, write an equation for L in terms of W. Solve the equations from parts a and b. Part c: The length is ? Cm. Part d: The width is? Cm.

Answers

Answer: (a) P = 6W + 2

(b) L = 2W + 1

(c) Width = 13cm

Length = 27cm

Step-by-step explanation:

The formula for perimeter of a rectangle is 2(length + width). Since the length is 1 cm more than twice its width, then the length will be:

L = (2 × W) + 1

(b) L = 2W + 1

Therefore, P = 2(L + W)

P = 2( 2W + 1) + 2W

P = 4W + 2 + 2W

(a) P = 6W + 2

Since perimeter is given as 80cm. Therefore,

P = 6W + 2

6W + 2 = 80

6W = 80 - 2

6W = 78

W = 78/6

W = 13

Width is 13cm

Length = 2W + 1

Length = 2(13) + 1

Length = 27cm

The width of the rectangle is 13cm and the length is 27cm.

Description of a rectangle

A rectangle is a quadrilateral. Opposite sides are equal. The four angles in a rectangle is equal to 90 degrees.

The formula for determining the perimeter of a rectangle = 2x (length + width)

P = 2(L + W)

Perimeter = 80 length = 1 + 2w Width = w

Determining the values of width and length

80 = 2(1 + 2w + w)

80 = 2(1 + 3w)

40 = 1 + 3w

40 - 1 = 3w

39 = 3w

w = 13cm

Length = 1 + 2(13) = 27cm

To learn more about rectangles, please check: https://brainly.com/question/16595449

CH 2. PPLYNOMIALS 1. The number 0 is called a​

Answers

Step-by-step explanation:

The number 0 is called a. zero polynomial. binomial.

zigya

Maths problem
Mass

Solve the problems below.

1. A box has 3 books. Each book has a mass of 250g.

(a) What is their total mass? ​

Answers

Answer:

250 x 3 = 750g

750g is your final answer

You have to multiply 250 by 3 because each book weighs 250g and you have three books.
Therefore the answer is 750g

if f(x)= 3^x+10x and g(x)= 2(x) = 2x - 4 find (f+g)(x)

Answers

Answer:

(f + g)(x) = 3^x + 12x -4

Step-by-step explanation:

Here, we want to get the value of (f + g)(x)

Mathematically, we have this as;

(f + g)(x) = f(x) + g(x)

= 3^x + 10x + 2x-4

= 3^x + 12x -4

Hey guys please try this is kinda urgent. what is the value of x in the geometric progression. 16/9 , x, 1, y.​

Answers

Answer: Either 4/3 or -4/3

============================================================

Explanation:

Let r be the common ratio. Also, we'll make r nonzero, i.e. [tex]r \ne 0[/tex]

Multiplying this common ratio by any term gets us the next term of the geometric sequence.

16/9 is the first term, so that makes (16/9)*r the second term

Since (16/9)r is the second term, the third term is (16/9)r*r = (16/9)r^2

Set this equal to 1 and solve for r.

(16/9)r^2 = 1

r^2 = 1*(9/16)

r^2 = 9/16

r = sqrt(9/16) or r = -sqrt(9/16)

r = 3/4 or r = -3/4

Now that we know what r is, we can determine the second term

If r = 3/4, then,

(16/9)*r = (16/9)*(3/4) = 4/3

Or if r = -3/4, then,

(16/9)*r = (16/9)*(-3/4) = -4/3

So the second term is either 4/3 or -4/3 depending on which r value you go for.

the value of x-y+xy if x=1 y=1 is

Answers

Answer:

1

Step-by-step explanation:

x-y+xy=1-1+1*1=0+1=1

Answer:

1

Step-by-step explanation:

X=1

Y=1

here,

x-y+xy=1-1+1×1

or,x-y+xy=0+1=1

Staysafe❤

the ratio of boys to girls is 4:3 .if there are 24boys ,how many are there?​

Answers

Answer:

[tex]{ \bf{total \: ratio = 4 + 3 = 7}} \\ { \tt{let \: population \: be \: p}} \\ \frac{4}{7} \times p = 24 \\ 4p = 168 \\ p = 42 \\ { \bf{there \: are \: 42 \: people}}[/tex]

Boys to girls- 4:3

Boys and girls- 24 and x (let the girls be x)

4/3=24/x

=4x= 72

= x= 72/4

= x= 18 girls

Ans: There are 42 children (24+18)

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