Tài liệu Database Systems: The Complete Book- P3 pptx

Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. [...]... design, and the class is usually named for the first ship of that class The relation C l a s s e s records the name of thr class, the type (bb for battleship or bc for battlecruiser), the country that built the ship, the number of main guns, the bore (diameter of the gun barrel, in inches) of the main guns, and the displacement (weight, in tons) Relation Ships records the name of the ship, the name of... s the in each attribute: i r ~ schema of S Since r and s are successfully paired, the joined tuple is able to agree with both these tuples on the attributes they have in common The construction of the joined tuple is suggested by Fig 5.5 R In this example, the first tuple of R successfully pairs with only the first tuple of S ; they share the value 2 on their common attribute B This pairing ~ields the. .. PC the speed (of the processor, in megahertz), the amount of RAM (in megabytes), the size of the hard disk (in gigabytes), the speed and type of the removable disk (CD or DVD), and the price The Laptop relation is similar, except that the screen size (in inches) is recorded in place of information about the removable disk The Prinzer relation records for each printer model whether the printer produces... schema of R and the schema of S Then a tuple r from R and a tuple s from S are successfully paired if and only if r and s agree on each of the attributes ill, A*, ,A, If the tuples r and s are successfully paired in the join R w S, then the result of the pairing is a tuple, called the joined tuple, with one component for each of the attributes in the union of the schemas of R and S The joined tuple... Ships b) Find the ships launched prior to 1921 c) Find the ships sunk in the battle of the North Atlantic d) The treaty of Washington in 1921 prohibited capital ships heavier than 33,000 tons List the ships that violated the treaty of Washington e ) List the name, displacement, and number of guns of the ships engaged it1 the battle of Guadalcanal f ) List all the capital ships mentioned in the database. .. tuple t Then the expression on the left has one t , while the expression on the right has none As sets, neither would have t Some exploration of algebraic laws for bags appears in Exercises 5.3.4 and 3.3.5 (a) The relation R (b) The relation S (c) The product R x S That is, all but the first tuple nieets the selection condition The last two tuples I which are duplicates in R , are each included in the. .. that the third column is called insours, which fits with the column header length in the second column Every tuple in the answer [%-ill have the constant h r s in the third column, which gives the illusion of being the units attached to the value in the second column 0 6.1.2 'Thus, the keyword SELECT in SQL actually corresponds most closely to the projection operator of relational algebra, while the. .. explicitly renames relations We shall use the operator PS(A~,A~, ,A,)(R) to rename a relation R The resulting relation has exactly the same tuples as R, but the name of the relation is S lloreover, the attributes of the result relation S are named dl: Iz, order from the ,.A,? in left If we only want to change the name of the relation to S and leave the attributes as they are in R, we can just say ps(R)... that is, they fail to match any tuple of the other relation in the common attributes Dangling tuples do not have any trace in the result of the join, so the join may not represent the data of the original relations completely In cases where this behavior is undesirable, a variation on the join, called "outerjoin," has been proposed and appears in various commercial systems IVe shall consider the "natural7'... as part of the answer The * in this example indicates that the entire tuple is produced The result of the query is the relation consisting of all tuples produced by this process One way to interpret this query is to consider each tuple of the relation mentioned in the F O clause The condition in the W E E clause is applied RM HR HR to the tuple SIore precisely?any attributes ment,ioned in the W E E