COP 4710 Study Guide - Comprehensive Final Exam Guide - Database Schema, Debtor, Unique Key
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An environment that is both convenient and efficient to use. *in the early days, database applications were built directly on top of file systems . *drawbacks of using file systems to store data: z data redundancy and inconsistency. Multiple file formats, duplication of information in different files z difficulty in accessing data. Hard to add new constraints or change existing ones z atomicity of updates. Failures may leave database in inconsistent state with partial updates carried out. Example: transfer of funds from one account to another should either complete or not happen at all z concurrent access by multiple users. Example: two people reading balance and updating it at the same time z security problems. Hard to provide user access to some, but not all, data . *database systems offer solutions to all the above problems. *physical level: describes how a record (e. g. , customer) is stored.