Databases Demystified a self teaching guide phần 5 pot

... redundant data in tables • Storing summarized data in tables Note also that normalization is intended to remove anomalies from databases that are used for online transaction-processing systems. Databases ... Databases that store historical data used solely for analytical purposes are not as subject to insert, update, and de - lete anomalies. Chapter 12 contains more information on data...

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... screen Constraints A constraint is a rule placed on a database object (typically a table or column) that restricts the allowable data values for that database object in some way. These are most important ... relational databases were built by both IBM and UC Berkeley. e. Nearly all the commercial relational databases are descendents of either System R or INGRES. 18. Currently avai...

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... row are called aggregate functions. The following table shows aggregate functions that are commonly used in relational databases: Function Name Description AVG Calculates the average value for a ... printer profile Composite Default screen 78 Databases Demystified Demystified / Databases Demystified / Oppel/ 2 253 64-9 / Chapter 3 beauty of relational databases is that we need n...

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... models, a brief his - tory of databases, and the rationale for focusing on the relational model. Properties of a Database A database is a collection of interrelated data items that are managed as a ... database can be defined as the file that contains the data items. Oracle Corporation defines their database as a collec - tion of physical files that are managed by an instance of...

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... that ends every SQL statement. In Oracle, a transaction is automatically started for each database user session as soon as the user connects to the database. At any time, the database user can ... table’s data. The ALTER TABLE Statement The ALTER TABLE statement may be used to change many aspects of the definition of a database table. Again, there is a wide variation in implementation a...

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... profile Composite Default screen 194 Databases Demystified Demystified / Databases Demystified / Oppel/ 2 253 64-9 / Chapter 7 The Data Flow Diagram The data flow diagram (DFD) is the most data centric of all the ... normalization is a. To eliminate redundant data b. To remove certain anomalies from the relations c. To provide a reason to denormalize the database d. To optimize dat...

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... complicated joins and calculations from the database users. For example, views can easily calculate ages based on birth dates, and they can summarize data in nearly any way imaginable. 220 Databases ... considered a best practice because it can lead to a lack of data sharing. Moreover, placing geographic or organizational unit names in table names plays havoc every time the organization...

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... even to a different version of the same vendor’s database). Connecting Databases to Java Applications Java started as a proprietary programming language (originally named Oak) that was developed ... that binds the API to the particular database and platform, and a definition known as the ODBC data source contains the information necessary for a particular application to connect with...

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... screen CHAPTER 12 Databases for Online Analytical Processing 301 Demystified / Databases Demystified / Oppel/ 2 253 64-9 / Chapter 12 Data Marts A data mart is a subset of a data warehouse that supports ... contains more data than a data warehouse. e. The project has a lower overall cost than a data warehouse project. 16. Building a data warehouse first, followed by data...

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... 259 –263 cookies, 257 – 258 data encryption, 256 – 257 database access, 258 –267 database clients and application security, 255 – 258 login credentials, 256 in Microsoft SQL Server, 259 –261 monitoring and auditing, ... 62–63 D Data Control Language (DCL), 90, 122–124 Data Definition Language (DDL), 90, 118–122 data encryption, 256 – 257 data flow diagram, 194–196 data integrity, 214 Da...

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