Below c level an introduction to computer systems

... characters, and have ASCII codes Since ASCII codes are taken from numbers in the range to 27 − = 127, each code consists of seven bits The EBCDIC system consists of eight bits, and thus can code ... 11000111000001110000000100000000, means to put the value into a certain cell of the computer s memory The circuitry in the computer is designed to recognize such patterns and act accordin...

Ngày tải lên: 19/11/2015, 15:07

... Forms Semantic Modeling Part IV : Transaction Management 15 Recovery 16 Concurrency Copyright (c) 2003 C J Date page fm.3 Part V : Further Topics 17 18 19 20 21 22 23 24 Security Optimization Missing ... need to come back and deal with it properly before you cover Chapter 20 or Chapters 2 5-2 7 • Read Chapter 11 "once over lightly." • Read Chapters 12 and 14 carefully,...

Ngày tải lên: 06/08/2014, 01:21

... required stored record occurrences; next, construct the required conceptual record occurrences; finally, construct the Copyright (c) 20 03 C J Date page 2. 5 required external record occurrence At each ... Farrell', 20 00, 12 , 20 05 ) ; 1. 9 No answer provided Copyright (c) 20 03 C J Date 1. 12 page *** End of Chapter *** Copyright (c) 20 03 C J Date page 1. 13 C...

Ngày tải lên: 06/08/2014, 01:21

... INTO :CJ _J# , :CJ_JN, :CJ_JC ; print CJ _J# , CJ_JN, CJ_JC ; END DO ; EXEC SQL CLOSE CJ ; END DO ; EXEC SQL CLOSE CS ; 4.6 The basic problem here is this: We need to "explode" the given part to n ... rows accessible via CS ; EXEC SQL FETCH CS INTO :CS_S#, :CS_SN, :CS_ST, :CS_SC ; print CS_S#, CS_SN, CS_ST, CS_SC ; EXEC SQL OPEN CJ ; DO for all J rows accessible via CJ ; EXEC SQL FETC...

Ngày tải lên: 06/08/2014, 01:21

... THE_R ( C ) ) ; END OPERATOR ; OPERATOR CIRCUMFERENCE ( C CIRCLE ) RETURNS LENGTH ; RETURN ( 3 . 14 159 * DIAMETER ( C ) ) ; END OPERATOR ; OPERATOR AREA ( C CIRCLE ) RETURNS AREA ; RETURN ( 3 . 14 159 ... some of the implications: Can't specify "uniqueness" on columns containing such values Can't joins over such columns Can't GROUP BY on such columns And so on Forward reference to...

Ngày tải lên: 06/08/2014, 01:21

... warehouse in city CITY • J: Project J# is under way, is named JNAME, and is located in city CITY • SPJ: QTY Supplier S# supplies part P# to project J# in quantity ────────── * For some unspecified reason! ... operators that together satisfy certain Copyright (c) 2003 C J Date page 7 .1 axioms or laws, such as the laws of closure, commutativity, associativity, and so on (closure...

Ngày tải lên: 06/08/2014, 01:21

... PCITY =/ CITY AS SCITY ) TIMES CITY AS PCITY ) TIMES CITY AS JCITY ) ) PCITY JCITY Copyright (c) 2003 C J Date SCITY ) TIMES PCITY ) TIMES JCITY ) ) { S#, P#, J# } page 7 .14 AND JCITY =/ SCITY ) ... RENAME CITY AS JCITY ) ) { SCITY, JCITY } 7.24 ( J JOIN SPJ JOIN S ) { P# } 7.25 ( ( ( J RENAME CITY AS JCITY ) JOIN SPJ JOIN ( S RENAME CITY AS SCITY ) ) WHERE JCITY =/ SCITY ) { J#...

Ngày tải lên: 06/08/2014, 01:21

... 300 ) AND SPJX.QTY ≤ QTY ( 75 0 ) 8 .13 . 17 { PX.COLOR, PX.CITY } Copyright (c) 2003 C J Date 8 .11 page 8 .13 .18 { SX.S#, PX.P#, JX .J# } WHERE SX.CITY = PX.CITY AND PX.CITY = JX.CITY 8 .13 .19 { SX.S#, ... 'London' AND PX.COLOR = COLOR ( 'Red' ) AND SPJX.S# = SX.S# AND SPJX.P# = PX.P# AND SPJX .J# = JX .J# ) Copyright (c) 2003 C J Date 8 .13 page 8 .13 . 41 JX .J# WHERE FORA...

Ngày tải lên: 06/08/2014, 01:21

... S.CITY, UPDATE on SPJ.S#, UPDATE on SPJ.QTY p UPDATE on SPJ.QTY q UPDATE on S.CITY 9.5 a Accepted b Rejected (candidate key uniqueness violation) c Rejected (violates RESTRICT specification) d Accepted ... FORALL JX EXISTS SX ( SX.CITY = JX.CITY ) ; i CONSTRAINT I FORALL JX EXISTS SX EXISTS SPJX ( SX.CITY = JX.CITY AND SX.S# = SPJX.S# AND SPJX .J# = JX .J# ) ; j CONSTRAINT J EXISTS PX (...

Ngày tải lên: 06/08/2014, 01:21

... P.CITY ; 10 .18 .3 CREATE VIEW SP AS SELECT SPJ.S#, SPJ.P#, SUM ( SPJ.QTY ) AS QTY FROM SPJ GROUP BY SPJ.S#, SPJ.P# ; 10 .18 .4 CREATE VIEW JC AS SELECT J. J#, J. CITY FROM J WHERE J. J# IN ( SELECT ... former──but we must be clear And then does "inherently many -to- one" mean, specifically, a foreign-key -to- matching-candidate-key join, or are there other cases that are inherently ma...

Ngày tải lên: 06/08/2014, 01:21

... two 11 .12 The first step is to rewrite the given set such that every FD has a singleton right side: AB C BC ACD BE CE CE → → → → → → → C A D B C A F Copyright (c) 2003 C J Date page 11 .7 11 11 CF ... B, C, D appears on the right side of any of the given FDs, it follows that {A,B ,C, D} is a candidate key Copyright (c) 2003 C J Date page 11 .9 *** End of Chapter 11...

Ngày tải lên: 06/08/2014, 01:21

... Copyright (c) 20 03 C J Date 12 . 12 page However, JOB2A is a projection of SALHIST2 (see below), and JOB2B is a projection of EMP1 (renamed as EMP2 below), so both of these relvars can be discarded ... again • JS JOIN SP yields the spurious tuple (S1,P2 ,J2 ); there's no (P2 ,J2 ) tuple in PJ; hence the final result is SPJ once again Copyright (c) 20 03 C J Date page 13 .4 Th...

Ngày tải lên: 06/08/2014, 01:21

... SPJ { S#, P# } JOIN SPJ { P#, J# } JOIN SPJ { J# , S# } ; Calculus version: CONSTRAINT SPJ_JD SPJ = { SPJX.S#, SPJY.P#, SPJZ .J# } WHERE SPJX.P# = SPJY.P# AND SPJY .J# = SPJZ .J# AND SPJZ.S# = SPJX.S# ... CTX (algebraic version): Copyright (c) 20 03 C J Date page 13.8 CONSTRAINT CTX_MVD CTX = CTX { COURSE, TEACHER } JOIN CTX { COURSE, TEXT } ; Calculus version: CONSTRAINT CTX_MVD CTX...

Ngày tải lên: 06/08/2014, 01:21

... three UPDATE operations U1, U2, U3, again not necessarily in that order.) Ri-Rj-Rk-Up-Uq-Ur Ri-Rj-Up-Rk-Uq-Ur Ri-Rj-Up-Uq-Rk-Ur Ri-Up-Rj-Rk-Uq-Ur Ri-Up-Rj-Uq-Rk-Ur : : : : : 3 3 * * * * * 2 1 * ... T1-T2-T3 T1-T3-T2 T2-T1-T3 T2-T3-T1 : : : : : A A A A A = = = = = 2 Copyright (c) 20 03 C J Date page 16.6 T3-T1-T2 T3-T2-T1 : A = : A = Of course, the six possible correct results ar...

Ngày tải lên: 06/08/2014, 01:21

... internal form Convert to canonical form Choose candidate low-level procedures Generate query plans and choose the cheapest In practice, Stage effectively becomes "convert the SQL query to a relational ... Divide-and-Conquer Strategy This section describes the historically important Ingres query decomposition approach and can serve as a springboard for getting into specifics of other trick...

Ngày tải lên: 06/08/2014, 01:21