Midterm Part B
A major key can also be known as a primary key which is a collection of columns in a table where all columns are functionally dependent on one another. Meanwhile a minor sort key which can also be referred to as secondary sort key is commonly known as the less important field, it is the less important part of the two creating one of their biggest key differences here is some more key differences between the two as well as a little bit of extra information as to their background. You can sort records using more than one field when necessary . When someone is trying to sort records by more then just one field the first sort field is always the major sort key also known as primary sort key. And the second sort field is knows as the minor sort key. It is also referred to as to as the secondary sort key. Another difference between the two different keys is their position when sorting query results using more than one field. For example the leftmost sortkey in the design grid is the major sort key, and the sort key to its right is the minor sort key once again this is a small difference but still a difference between the two.
2. In access a validation rule is a rule that data entered in a field must satisfy if it does not then the user get validation text which is a message that is displayed when a validation rule is violated. If a user doesn’t meet specified validation rules then they cannot save whatever they are doing until the errors are corrected and follow the validation rules indicated by the person who specified them. A validation rule also can contain a formula that evaluates data entered into field by the user and and can return a value of true or false back to the user in the form of validation text. There are two different ways to create a validation rule, the first way is to open the table in design view and then click in the field row and type out the expression in the validation rule box. The second way is first open the form in design view then right click the control and click properties. Then on the data tab type the expression in the validation rule box. Validation rule and validation text are extremely important to a database because without them the user or users could potentially make mistakes and not be notified of them therefore the mistakes would eventually add up and could potentially create a total database failure meaning all user would receive errors when working with the database. This is why the usage of validation rules as well as validation text is extremely crucial and highly recommended.
3. There are several reasons as to why the impact of failure in database processing is much greater when compared to the nondatabase apporach. One is the increased complexity of the database processing for example if a sufficient database fails then there would be a need for an even more complex and more efficient database to be created which can be very hard as well as extremely complex based on the amount of users a certain database may hold. On the subject of user that is actually the next reason as to why the impact of failure hits harder when working with database processing. For example in a nondatabase oriented system each user would have their own separate system so if there happened to be a a single failure with a single user then none of the other users would be affected by this failure and it would be fairly easy to fix. However if their are several users sharing the same database if a failure would happen to occur then it would potentially affect all connected users creating a widespread problem that require much more work and time to fix. These problems are quite common within databases and can happen often.
4. A null is a special value that represent the absence of a value in a field. Nulls are used when a value is either unknown or inapplicable. A null may also be referred to as a special marker used in SQL to indicate that a default value does not exist within the database itself. A null value within a database is not the same as a value of zero. Zero is a value for an integer so it has a meaning. Meanwhile NULL has a literal meaning of nothing so therefore it provides no value to the database structure. Null is a non value it is nothing more than a placeholder for a data value that is not yet known or specified within the database. A null should be used in a database whenever the actual value is unknown or simply does not exist. Sometimes this can happen in a database overtime such as someone who moves and forget to give their employer their new address however the employer knows about the move. Instead of keeping it the same and sending postal packages to the wrong address the employer should just correct the value to null until the employer is able to update their postal information.
5. An aggregate function is commonly known as a function used to calculate the number of entries as well as the sum or average of any entries given within a particular column. Or the largest or smallest of the entries given within a particular column also commonly referred to as a function. Access as well as any other products that may support QBE have support within for the following functions known as aggregate function within when working in access. Avg which stands for average, CountSum,Max which refers to the largest value within the database,StDev which stands for standard deviation variance ,Min which refers the smallest value within the database, First and last. In order to use any of the aggregate functions mentioned above within a query, you must include them in the total row for the column in the design grid. The total row does not appear on its own within the design grid. You must click the total button in the show hide group on the query tools design tab. Once you have done this any changes you have made to you database using any of the six available aggregate to Access will be able to be seen by the user and anyone else using the databases.
6. Database processing compared to any other form of keeping track of data entrys as well as maintaining those entrys in an ogranzied fashion along with quick access to those files is far superior than almost any other form of data management. Database processing comes with so many advantages it is almost hard to see why anyone in the field of database management would not use access or some other form of an SQL to keep track of records. Some of these advantages include but are not limited to a much improved version of data sharing which allows users to share data within the database with other users, this comes in handy quite often when working with databases. Another pro or advantage is improved data security for very obvious reasons a good strong data security is extremely important to the user of the database so none of their critical information contained within the database may fall into the wrong hands. Also there is minimized data inconsistency as well as improved data access. These two advantages are also extremely valuable and important to the database process. Another advantage database processing has compared to the another choices is better data integration. What this means is that it is much easier for a user to integrate data within a database when using some form of a database processor. The last two advantages held by database processing are improved decision making and increased end user productivity. These last two advantages are just as helpful and important as the others listed above.
7. A client/server system is a type of architecture where a networked system located within a special site on the network known as the server provides services to other sites called clients.In other words within this alternative architecture the server is a computer providing data to all of its clients. Which can be a wide range of devices such as PC based computers, tablets or other mobile devices that people may connect to the network and access data stored within the server. Then a DBMS often already running on the connected server will view request sent by the other devices then process these request before sending back out the correct data and other results back to the connected devices. A stored procedure is often referred to as file containing within its documents a collection of compiled SQL statement that are available for future use. A stored procedure may also be referred to as simply an operation that is stored within the database server. Using stored procedures often results in increased efficiency within the client/server system. There are a few reasons as to why this is for example, if you happen to call a stored procedure from a client application it would result in much less network traffic within the network itself this is a very good thing. Another reason is because when using stored procedures there is a not only convenient but as well as a very effective security mechanism within it. This is very helpful to the user for obvious reasons.
8. A compound condition which is also referred to as compound criteria in the within the book is two simple criteria or conditions in a query that are combined with the OR or AND operators. The way a compound condition is formed is by connecting two or more simple conditions using either the AND or OR operators.This way of formation is unique to itself in that it is one of the only possible ways that a compound condition can be formed within the database itself. Whenever a user attempts to connect simple conditions using the AND operator all condition must be true in order for the compound to admit true. When a user attempts to connect simple conditions using the OR operator the compound condition will output true whenever any of the simple condition admit true. There is also the NOT operator to be aware of when talking about compound conditions and their different formation options. If the user attempts to submit a NOT operator before then the NOT operator will then reverse the result of the original condition therefore creating an entirely different result output for the user. For example if the original condition was true then it would be false and if the original condition was false then it would output true.
9. Redundancy is the duplication of data or it also is known as the storing of the same data in more than one place. Eliminating redundancy is usually always the best possible choice however, this is not always possible to do thanks to certain limitations for example one extremely common limitation is performance. So whenever given the option the user should almost always refer to the actions they do with redundancy as controlling rather than eliminate the redundancy. The pros of eliminating however heavily outweigh those of controlling. For example eliminating makes the process of updating much simpler. Also making changes like address, phone number and other often changed information within the database is much easier to accomplish because there is only one change required. On the other hand for controlling in which data for each client might be up to three different places. In which case you would have to manually go to each one to make one change. Which not only could possibly introduce multiple errors but also over time has the potential to add up and become over complicated if many people happen to be changing things such as their addresses. However even in these situations it is said that one must keep the redundancy under tight control. This is why it is much better and more common to simply say that the user controls redundancy rather than elimanting the redundancy.