Applied Mathematics for Database Professionals phần 10 doc

... 29 Cartesian product, 39 compatible functions, 77 database, 93 database design, 92 database management system (DBMS), 93 database state, 93 database universe, 92 database variable, 92 disjoint sets, 34 function ... 167–181 specification of, 325–330 specifying formally, 141 transactions and, 221–236 database variable, defined, 92 databases defined, 93 documenting, 140 Date, Chris,...

Ngày tải lên: 08/08/2014, 18:21

... (empno ;103 ), (ename;'Tedesco'), (mgrno ;104 ), (deptno ;10) } ,{ (empno ;104 ), (ename;'Rhodes'), (mgrno ;106 ), (deptno ;10) } ,{ (empno ;105 ), (ename;'Sparks'), (mgrno ;106 ), ... shorthand name for a given database universe (just symbols) for conven- ience of reference in the text. Database State Database state is a formal term. It is a mathematic...

Ngày tải lên: 08/08/2014, 18:21

... you to a formal way of specifying a database via a database state. Formal Representation of a Database State Let’s consider a simple database design involving two table structures: one for employees ... table, or database state satisfies them. However, when formally specify- ing a database design, we aren’t interested in a single database state (or table or tuple). We are inte...

Ngày tải lên: 08/08/2014, 18:21

... containers of DI code for table constraints. Before statement triggers see the start database state in which a DML statement starts execution. After statement triggers see the end database state created ... can formally derive the constraint validation query that you need to execute for verifying whether a new database state still satisfies this constraint. The way to do this is by...

Ngày tải lên: 08/08/2014, 18:21

... constraints, and formally specifies these for the given example database design. Chapter 9 shows how you can precisely formulate queries in mathematics , and Chapter 10 shows ho w you can formally specify ... visit http://en.wikipedia.org/wiki/ Orthogonality. xxv 7451FM.qxd 5/17/07 10: 41 AM Page xxv Applied Mathematics for Database Professionals Copyright © 2007 by Lex de...

Ngày tải lên: 08/08/2014, 18:21

... and therefore a source of confusion. The section “Normal Forms” discusses normal forms in logic—not to be confused with normal forms of data (defined for database design purposes). Normal forms ... following two normal forms for predicates: • Conjunctive normal form is a predicate rewritten in the format of an iterated AND. • Disjunctive normal form is a predicate rewritten in the forma...

Ngày tải lên: 08/08/2014, 18:21

... limit regarding database professionals, then there cannot be a result with an average score of A for database professionals (r egardless of the course), and if ther e is a limit regarding non -database professionals, ... of how you can formally specify a database design. Formalizing a database design specification has the advantage of avoiding any ambiguity in the documentatio...

Ngày tải lên: 08/08/2014, 18:21

... set of database states called the database universe. It holds the admissible database states for the database being specified. You can con- struct a database universe by first defining a database ... result by specifying database predicates. These database predicates are called database constraints. • This formal model is your—the database professional’s—reference of th...

Ngày tải lên: 08/08/2014, 18:21

... of a database; they enable you to extract infor- mation from a database that is relevant for you. • You can formally represent a query as a function over a database universe. For every database ... be inserted into the database: tcrs1 := { (CODE;'AM4DP') , (DESC;&apos ;Applied Mathematics for Database Professionals& apos;) , (CAT;'DSG') , (DUR;5) } Fo...

Ngày tải lên: 08/08/2014, 18:21

... ■ FORMAL DEFINITION OF EXAMPLE DATABASE3 14 7451AppA.qxd 5/15/07 9:45 AM Page 314 Formal Definition of Example Database In this appendix, we deliver the formal specification of the example database ... salary. We hold additional information for all sales representatives in a separate table ( SREP). We hold additional information for employees who no longer work for the company (tha...

Ngày tải lên: 08/08/2014, 18:21