Custom fields are fields that can contain the results of a formula or function
Indicate whether the statement is true or false
FALSE
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Assume that each individual SQL statement is executed in isolation, that the DBMS uses intention locking and sets locks on tables and rows, and that host variable f contains the number of the flight to be booked. The transaction should not overbook the flight.
An airlines database has two tables: Flights, with attributes flt_num, plane_id, num_reserv; and Planes, with attributes plane_id, and num_seats. The attributes have the obvious semantics. A reservation transaction contains the following steps:
SELECT F.plane_id, F.num_reserv INTO :p, :n FROM Flights F WHERE F.flt_num = :f A. SELECT P.num_seats INTO :s FROM Planes P WHERE P.plane_id = :p B. . . . check that n < s ... C. UPDATE Flights F SET F.num_reserv = :n + 1 WHERE F.flt_num = :f D. COMMITa. Assuming that the transaction is run at READ COMMITTED, w hat locks are held at points A, B, and D? b. The database can be left in an incorrect state if concurrently executing reservation transactions that are running at READ COMMITTED are interleaved in such a way that one transaction is completely executed at point B in the execution of another. Describe the problem. c. In an attempt to avoid the problem described in (b), the SET clause of the UPDATE statement is changed to F.num_reserv = F.num_reserv + 1. Can reservation transactions nowbe run correctly at READ COMMITTED? Explain. d. Assuming that the transaction is run at REPEATABLE READ and that the tables are accessed through indices, what table locks are held at points A, B, and D? e. What problem does the interleaving of (b) cause at REPEATABLE READ? Explain. f. Does the interleaving of (b) cause an incorrect state if the transaction (either version) is run using SNAPSHOT isolation? Explain. g. To keep track of each passenger, a newtable, Passenger, is introduced that has a rowdescribing each passenger on each flight with attributes name, flt_num, seat_id. SQL statements are appended to the end of the transaction (1) to read the seat_id’s assigned to each passenger on the flight specified in f and (2) to insert a rowfor the newpassenger that assigns an empty seat to that passenger. What is the weakest ANSI isolation level at which the transaction can be run without producing an incorrect state (i.e., two passengers in the same seat)? Explain.
You later decide that you want to add text to the photograph. You type in some text with the bounding box tool but quickly realize that the text takes up too much space on your photograph. What do you do to fix this problem?
a. Click the handles to reset the bounding box. b. Drag the handles to resize the bounding box. c. Hit ESC to cancel the effect. d. Rotate the bounding box.
What will be output from the following code:
____ sounds are useful when you need the animation in your movie to coincide with the sound.
A. Event B. Stream C. Action D. Index