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Trouble Spots

Trouble Spots

As with any exam, it will vary from person to person as to what is deemed to be difficult. Some of the topics you may have trouble with are Relational Databases, Data Definition Language (DDL), and Types of Backups.

Relational Databases

Originally, databases were flat, which means that the information was stored in one long text file. These files were often delimited with tabs or commas. Unfortunately, this is not an efficient way to store large amounts of data. The relational database is a series of databases or tables that are linked by a key that is common among the tables. By storing data in this way, no one table has all of the data.

For instance, you may use an employee number to identify a person. This allows you to have an employee table that lists all pertinent information about your employees without having to include the same information in all tables that reference employees. An Employee Table may contain the fields EmployeeNumber, EmployeeName, Address, City, State, ZipCode and Payrate. A Sales Table may include the fields EmployeeNumber, Item, SalePrice, and Quantity. The Sales Table includes the EmployeeNumber, which is the key that allows you to relate to the two tables together. This use of relational databases allows you to keep the size of your databases to a minimum by reducing redundant information. The downside of relational databases is that producing reports from multiple tables can prove more difficult than if all the information you need is in a flat database.

Data Definition Language (DDL)

Data Definition Language is a computer language for defining data structures. It can also be described as a standard for commands that define the different structures in a database. It describes the portion of SQL that allows you to create, alter, and delete database objects. Some of the database objects include schemas, tables, views, sequences, catalogs, indexes, and aliases. Microsoft Jet provides a full set of Data Definition Language SQL statements, which can be used to create, modify, and delete tables, indexes, and relationships in a Microsoft Access database file.

Types of Backups

A full backup will backup all of your data. A full backup takes longer than other types of backups, but is easier to restore. A differential backup will backup all of the data that has changed since the last full backup. An incremental backup will backup all data since the last incremental backup. An incremental backup is the quickest, but also requires the most time to restore.

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