Study Guide Mis 691 Chapter 2

Study Guide MIS 691 Midterm Chapter 2. 2 Entity: One topic or theme; something of significance to a client that should be spoken to in a database. In the substance relationship model, elements are confined to things that can be spoken to by a solitary table. A case of this is in the EMPLOYEE table; information about the substance (the worker) is in the table lines and information about the entity’s traits are in the lines. 2. Rundown the qualities a table must be a connection: * Each line of the table holds information that relate to some substance or a segment of some element * Each section contains information of the properties of the element * The cells must hold a solitary worth; no rehashing components * All of the passages in any segment must be a similar kind * Each segment must have an extraordinary name and the segment request is irrelevant * The request for the lines in immaterial * No two columns in the table may hold indistinguishable information esteems 2. 0 Defin e the term novel key and give a model: A key that characterizes a special column. A case of a one of a kind key in the EMPLOYEE table is EmployeeNumber; the inquiry of any EmployeeNumber (223 for instance) will just create a solitary line and information for one worker. 2. 11 Non-interesting key: A key that conceivably recognizes more than one line. In the EMPLOYEE table from our book, Department is a non-novel key since it distinguishes a few lines. 2. 12 Give a case of a connection with an exceptional composite key: A composite key contains at least two attributes.An case of a novel composite key in the EMPLOYEE table is in the event that we consolidated LastName, FirstName, and Department as a key; these three traits joined would safeguard that we would distinguish just one line. 2. 13 Explain the contrast between an essential key and a competitor key: Candidate keys will be keys that particularly recognize each line in a connection. They can be single or composite. The essential key is the applicant key that is picked as the key that the DBMS will use to remarkably recognize each column. 2. 5 What is a proxy key and under what conditions would you utilize one? A proxy key is a segment with an interesting, DBMS-allocated identifier that has been added to a table to be the essential key. You would utilize a substitute key when the essential key in the table isn't perfect. You include a proxy since it is short, numeric, and will never show signs of change †it is a perfect essential key. 2. 20 Define the term referential trustworthiness limitation and give a model: A relationship imperative on remote key values.A referential uprightness requirement determines that the estimations of an outside key must be a legitimate subset of the estimations of the essential key to which it alludes. In the EMPLOYEE table: the estimation of Department should coordinate an estimation of DepartmentName in the DEPARTMENT table. 2. 21 Explain the three potential translations of an invalid worth: 1. It could imply that no worth is fitting 2. It may imply that the worth is known to be clear (deliberately left clear) 3. It might imply that the worth is obscure 2. 4 Name the useful reliance and recognize the determinants of: Area = Length x Width Area is practically needy upon Length and Width or that the composite of Length and Width are determinants of Area 2. 31 Describe the nature and reason for the standardization procedure: Normalization is separating tables with more than one topic into sets of tables that have one topic each. You need to do this so that there isn’t rehash data in a table thus there are no adjustment or cancellation issues.Normalization: Normalization is the way toward breaking a table with at least one topic into a lot of tables to such an extent that each just has one topic. You have to make an all around framed connection: 1. Each determinant must be an up-and-comer key 2. Any connection that isn't all around framed ought to be broken into at least two relations that are very much shaped The Normalization Process: 1. Indentify the entirety of the up-and-comer keys 2. Indentify the entirety of the useful conditions 3. Analyze the dereminants of the useful dependencies.If any determinant isn't a competitor key, the connection isn't all around shaped. For this situation: a. Spot the segments of the useful reliance in another connection of their own b. Make the determinant of the useful dependacy the essential key of the new connection c. Leave a duplicate of the determinat as an outside key in the first connection d. Make a referential uprightness imperative between the orginal and the new connection. 4. Rehash stage 3 until each key is an up-and-comer key