中央大學。范錚強 1 從 ER 到 Logical Schema 國立中央大學 資訊管理系 范錚強 2002

中央大學。范錚強 2 準備 Logical Schema  資料模型和流程模型的整合  充實、調整資料模型  設計關連式資料庫 Logical Schema

中央大學。范錚強 3 設計關連式資料庫 Logical Schema  For each entity type:  Each Entity type becomes a Table  Every attribute becomes a column  The identifying attribute for the entity type becomes the key for the Table  For each m-n relationship type  Each m-n relationship type becomes a Table  Every attribute becomes a column  The identifying attribute of the associated entity types becomes the compound keys

中央大學。范錚強 4 資料模型和流程模型的整合  修訂模式  修改 DFD 中的 data store ，消除所有「迷糊帳」  所有 data store 相對到相關的實體或關係  建立資料典 DD:Data Dictionary  平衡 Balancing 原則  Every data flow and data store must be defined in the DD, Vice Versa  Every data store must correspond to an entity or relationship type  Object names in the DD, ERD and DFD must match  DD entries must apply to both the DFD and ERD model

中央大學。范錚強 5 資料模型、邏輯資料庫設計、實 體資料庫設計  Process  E-R data model --> Logical database design --> physical database design  ANSI SPARC three tier DB architecture  Enterprise views  User views  Physical views Physical Enterprise user

中央大學。范錚強 6 充實、調整資料模型  Attributing and Refining  Attributing all entity and relationship types  Eliminate all multi-valued attributes with appropriate relationships  Identify an identifying attributes for each entity type and and any compound relationship

中央大學。范錚強 7 設計關連式資料庫 Logical Schema  For each entity type:  Each Entity type becomes a Table  Every attribute becomes a column  The identifying attribute for the entity type becomes the key for the Table  For each m-n relationship type  Each m-n relationship type becomes a Table  Every attribute becomes a column  The identifying attribute of the associated entity types becomes the compound keys

中央大學。范錚強 8 關連式資料庫 Logical Schema (2)  For each 1-n relationship type  Same as m-n relationship  Only the n-side identifier becomes the key, the 1-side identifier becomes a non-key column  For each 1-1 relationship type  Same as 1-n relationship  Pick the identifier from the appropriate associated entity type as the key, the other a non-key column

中央大學。范錚強 9 關連式資料庫 Logical Schema (3)  For each compound entity type  For the compound entity types that do not have its own identifier, same as relationship  Otherwise, use the identifier as the key, and take the identifying attribute of the associated entity types as non-key columns

中央大學。范錚強 10 其他限制  在 Compound Entity 中﹐若有任何相關的 entity type 的 identifier 必須相同﹐將相關的 key 去除  若有其他的限制﹐加入到 DBMS 中﹐資料的 integrity 或 referential constraints 中

中央大學。范錚強 11 實體資料庫設計  可考慮將單一欄位的 Table 取消  Referential constraints  Domain specification  深入了解 data behavior  合併或分解 Tables  Examine the properties and behavior of tables and data  Combine tables with the same key or same partial keys as appropriate (may result in lower normal forms)  Split a Table into multiple tables, to maximize operational efficiency