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WGU C175 STUDY NOTECARDS
Flat Files - Answers - a file having no internal hierarchy Hashed Files - Answers - A file that has been encrypted for security purposes. Heap File - Answers - An unsorted set of records. Information - Answers - The transformation of raw data into useful facts. Punch Card - Answers - A card that is perforated and can hold commands or data. Structured Data - Answers - Information with a high degree of organization. Unstructured Data - Answers - Information that does not have structure (such as text) Binary Relationship - Answers - A relationship between two entity types. Unary Relationship - Answers - An associate occurrence of an entity type with other occurrences of the same entity type. Cardinality - Answers - The maximum number of entities that can be involved in a particular relationship. E-R Model *E-R = Entity - Relationship - Answers - Diagram of entities together with their attributes and the relationship among them. Intersection Data - Answers - It is data that describes a many-to-many relationship. Modality - Answers - It is a minimum number of entity occurrences that can be involved in a relationship. One-to-one Binary Relationship - Answers - It means that a single occurrence of one entity type can be associated with a single occurrence of the other entity type and vice versa. Ternary Relationship - Answers - Involves three different entity types. Unique identifier - Answers - It is used to uniquely identify each record in a database table.
Attribute - Answers - A property, characteristic, or fact that we know about an entity. "A salesperson works in one office." What is the name of this relationship? - Answers - One-to-one binary relationship "A salesperson sells to many customers." What is the name of this relationship? - Answers - One-to-many binary relationship "A salesperson is authorized to sell many products, and a product can be sold by many salespersons." What is the name of this relationship? - Answers - Many-to-many binary relationship What is the positioning and meaning for Cardinality and Modality on an E-R model? - Answers - Cardinality is the outer symbol; represents the maximum. Modality is the inner symbol; represents the minimum. "A salesperson works in a minimum of one and a maximum of one office, and an office may be occupied by or assigned to a minimum of zero and a maximum of one salesperson." - Answers - "A salesperson may have no customers or many customers." - Answers - Describe the ER model for "Each salesperson is authorized to sell to at least one or many products, and each product can be sold by at least one or many salespeople." - Answers - "One salesperson backs-up another salesperson." What is the name of this model? - Answers - One-to-one unary relationship "A salesperson manages zero to many other salespersons, and a salesperson is managed by exactly one other salesperson." What is the name of this model? - Answers - One-to-many unary relationship "A product can either be part of no other products or be part of several other products, and a product can either be composed of no other products or be composed of several other products." What is the name of this model? - Answers - Many-to-many unary relationship
Tuple - Answers - Rows/records are referred to as tuples when talking about relations. They serve the exact same function, it just has a different name in the context of relations. What are the five basic principles of The Database Concept? - Answers - 1. The creation of a datacentric environment that is a significant company resource, which can be shared inside and outside the company.
- The ability to achieve data integration while storing data in a non-redundant fashion.
- The ability to store data representing entities involved in multiple relationships w/o introducing data redundancy.
- Managing data control issues such as data security, backup and recovery, and concurrency control.
- High degree of data independence. What are the four major DBMS approaches? - Answers - - Hierarchical
- Network
- Relational
- Object-oriented What are four key differences between a RELATION and a FILE? - Answers - - The columns of a relation can be arranged in any order w/o affecting the meaning of the data. That is not true of a file.
- Similarly, the rows of a relation can be arranged in any order, which is not true of a file.
- Every row/column position, sometimes referred to as a "cell", can have only a single value, which is not necessarily true in a file.
- No two rows of a relation are identical, which is not necessarily true in a file.
- in the SELECT clause - Answers - - It indicates that all attributes of the selected row are to be retrieved AND operator - Answers - - It displays a record if more than one condition is true AVG() function - Answers - - It returns the average value of a numeric column. BETWEEN operator - Answers - - It allows you to specify a range of numeric values in a search. DISTINCT operator - Answers - - It is used to eliminate duplicate rows in a query result. IN operator - Answers - - It allows you to specify a list of character strings to be included in a search JOIN clause - Answers - - It is used to combine rows from more than one table, based on a common field between them. Sometimes it is done by using the '=' symbol.
LIKE operator - Answers - - It allows you to specify partial character strings in a "wildcard" sense. OR operator - Answers - - It displays a record it either the first condition OR the second condition is true. ORDER BY clause - Answers - - It simply takes the result of a SQL query and orders them by one or more specified attributes. SELECT command - Answers - - Data retrieval in SQL is accomplished with the SELECT command. Subquery - Answers - - When on SELECT statement is "nested" within another in a format, it is known as subquery. This is shown when there is a second SELECT phrase within a set of parenthesis. Common DDL commands: - Answers - - DROP
- ALTER
- RENAME
- CREATE
- TRUNCATE Common DML commands: - Answers - - UPDATE
- DELETE
- INSERT
- MERGE
- SELECT Write the basic SQL query command: - Answers - SELECT FROM WHERE Write the SQL query to "Find the commission percentage and year of hire of salesperson 186": - Answers - SELECT COMMPERCT, YEARHIRE FROM SALESPERSON WHERE SPNUM=186; Write the SQL query to "Retrieve the entire record for salesperson 186": - Answers - SELECT * FROM SALESPERSON WHERE SPNUM=186; Write the SQL query to "List the salesperson numbers and salesperson names of those salespersons who have a commission percentage of 10.": - Answers - SELECT SPNUM, SPNAME FROM SALESPERSON
names within the same city alphabetized)": - Answers - SELECT CUSTNUM, CUSTNAME, HQCITY FROM CUSTOMER WHERE CUSTNUM> ORDER BY HQCITY, CUSTNAME; Write the SQL query to "Find the average quantity of units of the different products that Salesperson 137 has sold": - Answers - SELECT AVG(QUANTITY) FROM SALES WHERE SPNUM=137; Write the SQL query to "Find the total quantity of units of all products that Salesperson 137 has sold": - Answers - SELECT SUM(QUANTITY) FROM SALES WHERE SPNUM=137; Write the SQL query to "Find the name of the salesperson responsible for Customer Number 1525": - Answers - SELECT SPNAME FROM SALESPERSON, CUSTOMER WHERE SALESPERSON.SPNUM=CUSTOMER.SPNUM AND CUSTNUM=1525; Write the SQL query to "List the NAMES of the products of which salesperson Adams has sold more than 2000 units": - Answers - SELECT PRODNAME FROM SALESPERSON, PRODUCT, SALES WHERE SALESPERSON.SPNUM=SALES.SPNUM AND SALES.PRODNUM=PRODUCT.PRODNUM AND SPNAME='Adams' AND QUANTITY>2000; CREATE TABLE command - Answers - The command that creates base tables and tells the system what attributes will be in them. CREATE VIEW command - Answers - Specifies the base tables on which the view is to be based and the attributes and rows of the table that are to be included in the view. DELETE command - Answers - Specify which row(s) of a table are to be deleted based on data values within those rows. DROP TABLE command - Answers - Discards an entire table from a database. DROP VIEW command - Answers - Discards views. Normalization - Answers - The process of organizing the fields and tables of a relational database to minimize redundancy (duplication) and dependency.
Second Normal Form - Answers - All non-key attributes must be functionally dependent on the entire key of that table. Third Normal Form - Answers - Non-key attributes are not allowed to define other non- key attributes. What are three important points about Third Normal Form? - Answers - 1. It is completely free of redundancy
- All foreign keys appear where needed to logically tie together related tables.
- It is the same structure that would have been derived from a properly drawn entity- relationship diagram of the same business environment. Write the SQL query to "Add a new salesperson into the SALESPERSON table whose salesperson number is 489, name is Quinlan, commission percentage is 15, year of hire is 2011, and department number is 59.": - Answers - INSERT INTO SALESPERSON VALUES ('489','Quinlan',15,'2011','59'); *Hint, this is DML, so remember that INSERT is one of the keywords for DML. Write the SQL query to "Delete the row for salesperson 186 from the SALESPERSON table.": - Answers - DELETE FROM SALESPERSON WHERE SPNUM = '186'; What is the correct syntax of the INSERT command? - Answers - INSERT INTO table_name VALUES (value1,value2,value3,...): What is the correct syntax of the CREATE VIEW command? - Answers - CREATE VIEW view_name AS SELECT column_name(s) FROM table_name WHERE condition What is called a decomposition process? - Answers - Data normalization In which of the normal forms should every non-key attribute be fully functionally dependent on the entire key of a table? - Answers - Second form What is the correct syntax of the CREATE TABLE command? - Answers - CREATE TABLE table_name ( column_name data_type(size), ); What is the correct syntax of the UPDATE command? - Answers - UPDATE table_name SET column1=value1,column2=value2,... WHERE some_column=some_value;
What is the key factor based on the need for linear scalability? - Answers - Performance What is used for populating summaries or any cube dimensions that can be performed at the staging area (ETL)? - Answers - Aggregation What data mining activity is a process of assigning some continuously valued numeric value to an object? - Answers - Estimation What includes exploiting the discovery of table and foreign keys for representing linkage between different tables? - Answers - Integration What data mining activity is the process of organizing data into predefined classes? - Answers - Classification Which activity groups data members that have similarities? - Answers - Clustering Data Warehouse - Answers - A data warehouse is the primary source of information that feeds the analytical processing within an organization. Data Mart - Answers - A data mart is a subject-oriented data repository, similar in structure to the enterprise data warehouse, but it's main purpose is to serve directed reporting and drill down into specific data. OLAP - Answers - OLAP (Online Analytical Processing) is both a process of viewing comparative metrics via a multidimensional analysis of data and the infrastructure to support that process. OTAP - Answers - OTAP (online transaction processing) provides a means for presenting data sourced from a data warehouse or a data mart in a way that allows the data consumer to view comparative metrics across multiple dimensions. Cartesian product - Answers - Usually the result of a missing join condition or a method of expanding the data of 1 table by the number of rows in the second table. Data volatility - Answers - Describes how often stored data is updated. DCL - Answers - Data control language is used to control access to data stored in a database. Definer - Answers - Definer is a MySQL term where AuthID is the same for another DBMS Domain of values - Answers - The shared values between a primary key and foreign key.
Extraction essentially boils down to two questions: - Answers - 1. What data should be extracted?
- How should that data be extracted? Inner join - Answers - Shows row that have matches in both tables Logical view - Answers - Logical view is a mapping onto a physical table or tables that allows an end user to access only a specified portion of data. Outer join - Answers - Shows rows in one table that have no match in the other table. Two kinds of outer joins are left and right joins. Referential Integrity - Answers - Referential integrity is a database concept that ensures that relationships between tables remain consistent. Response Time - Answers - Is the delay from the time that the Enter Key is pressed to execute a query until the result appears on screen. Scalar subquery - Answers - Is the most restrictive subquery because it produces only a single value Superkey - Answers - A superkey is any number of columns that forces every row to be unique. Throughput - Answers - Is the measure of how many queries from simultaneous users must be satisfied in a given period of time by the application set and the database that it supports. UNION - Answers - To create a result set that combines the results from several queries What are 6 potential problems that need to be considered with databases? - Answers -
- Size
- Ease of updating
- Accuracy
- Security
- Redundancy
- Importance
