5/2/2023 0 Comments Subversion ddo![]() ![]() In the simplified data model for this tutorial, a single relational model reflects the entire logical model however, for other data models you can create one or more relational models, each reflecting all or a subset of the logical model. The relational model for the library tutorial database consists of tables that reflect the entities of the logical model (Books, Patrons, and Transactions) and all attributes of each entity. Optionally, double-click a line (or right-click a line and select Properties) and view the Relation Properties information.ĭata Modeler Tutorial: Modeling for a Small Database A line with an arrowhead is drawn from Patrons to Transactions. A line with an arrowhead is drawn from Books to Transactions.Ĭlick first in the Patrons box, then in the Transactions box. Suggestion: Turn off auto line routing for this exercise: right-click in the Logical pane, and ensure that Auto Route is not checked.Ĭlick first in the Books box, then in the Transactions box. (If the pointer is still cross-hairs, click the Select icon at the top left to change the pointer to an arrow.) In the logical model pane in the main area, arrange the entity boxes as follows: Books on the left, Patrons on the right, and Transactions either between Books and Patrons or under them and in the middle. Note that for this figure, Bachman notation is used (you can change to Barker by clicking View, then Logical Diagram Notation, then Barker Notation).ĭescription of the illustration lib_logical_diagram.gif When you are done, the logical model pane in the main area should look like the following figure. Each patron can check out one or many books in a visit to the library, and can have multiple active checkout transactions reflecting several visits each patron can also return checked out books at any time.Ĭreate the relationships as follows. Each patron can be involved in multiple sequential and simultaneous transactions. Each book can have zero or one active checkout transactions a book that is checked out cannot be checked out again until after it has been returned. Each book can be involved in multiple sequential transactions. The following relationships exist between the entities:īooks and Transactions: one-to-many. Relations show the relationships between entities: one-to-many, many-to-one, or many-to-many. Click Add to start each definition, and click Apply after each definition. In the Domains Administration dialog box, add domains with the following definitions. (These added domains will also be available after you exit Data Modeler and restart it later.)Ĭlick Tools, then Domains Administration. You therefore decide to add appropriate domains, so that you can later use them to specify data types for attributes when you create the entities. Titles (books, articles, and so on) can be up to 50 characters. Other identifiers are numeric, with up to 7 digits (no decimal places). Zip codes (United States postal codes) can be up to 10 characters ( nnnnn- nnnn).īook identifiers can be up to 20 characters. State codes (United States) are 2-character standard abbreviations. Street address lines can be up to 40 characters. The first and last names of persons can be up to 25 characters each. In planning for your data needs, you have determined that several kinds of fields will occur in multiple kinds of records, and many fields can share a definition. You will perform the following major steps: ![]() ![]() (For information about the approaches, see Approaches to Data Modeling.) This simplified tutorial uses only a subset of the possible steps for the Top-Down Modeling approach. If the instructions do not mention a particular dialog box, tab, or field, then do not specify anything for it. For more advanced tutorials and other materials, see For More Information About Data Modeling. The model is deliberately oversimplified and would not be adequate for any actual public or organizational library. This tutorial uses the same entities as for the tutorial provided with the SQL Developer online help. ![]() In this tutorial, you will use Data Modeler to create models for a simplified library database, which will include entities for books, patrons (people who have library cards), and transactions (checking a book out, returning a book, and so on). ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |