Write the following as triggers. In each case, disallow or undo the modification if it does not satisfy the stated constraint. T
he problems are based on our running movie example:
Movies(title, year, length, genre, studioName, producerC#)
StarsIn(moveTitle, moveYear, starName)
MovieStar(name, address, gender, birthdate)
MovieExec(name, address, cert#, netWorth)
Studio(name, address, presC#)
You may assume that the desired condition holds before any change to the database is attempted. Also, prefer to modify the database, even if it means inserting tuples with NULL or default values, rather than rejecting the attempted modification.
a. Assure that at all times, any star appearing in StarsIn also appears in MovieStar.
b. Assure that at all times every movie executive appears as either a studio president, a producer of a movie, or both.
c. Assure that every movie has at least one male and one female star.
Movies(title, year, length, genre, studioName, producerC#)
StarsIn(moveTitle, moveYear, starName)
MovieStar(name, address, gender, birthdate)
MovieExec(name, address, cert#, netWorth)
Studio(name, address, presC#)
You may assume that the desired condition holds before any change to the database is attempted. Also, prefer to modify the database, even if it means inserting tuples with NULL or default values, rather than rejecting the attempted modification.
a. Assure that at all times, any star appearing in StarsIn also appears in MovieStar.
b. Assure that at all times every movie executive appears as either a studio president, a producer of a movie, or both.
c. Assure that every movie has at least one male and one female star.
1 answer:
You might be interested in
Answer:
4. The demand for gasoline-powered automobiles would increase and the equilibrium price of gasoline-powered automobiles would increase.
Explanation:
Substitute goods are goods that can be used in place of each other.
If the price of electric automobiles rises, the automobile becomes more expensive for consumers. Consumers would reduce the quantity demanded of the electric automobile and shift its demand to gas powered automobiles.
As a result, the demand for gas automobiles increases and the equilibrium price would increase too.
I hope my answer helps you
