wgu c175 vocab (questions and answers 2024).

E-R Model It is well named, as it diagrams entities (together with their attributes) and the relationship among them. Describe the ER model for "A salesperson works in one office." - What is the name of this relationship? exists when two entities are associated/relationship - Ex. A professor teaches many classes. - One-to-one binary relationship Brainpower Read More 0:02 / 0:15 Describe the ER model for "A salesperson sells to many customers." - What is the name of this relationship? 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. - One-to-many binary relationship Describe the ER model for "(L to R) A salesperson is authorized to sell many products; (R to L) a product can be sold by many salespersons." - What is the name of this relationship? - Many-to-many binary relationship What is the positioning and meaning for Cardinality and Modality on an ER model? - Cardinality is the outer symbol; represents the maximum. - Modality is the inner symbol; represents the minimum. Describe the ER model for "(L to R) A salesperson works in a minimum of one and a maximum of one office, or exactly one office." "(R to L) An office may be occupied by or assigned to a minimum of no salespersons or a maximum of one salesperson." Describe the ER model for "A salesperson may have no customers or many customers." Describe the ER model for "(L to R) Each salesperson is authorized to sell to at least one or many of our products."and "(R to L) Each product can be sold by at least one or many of our salespersons." Describe the ER model for "One salesperson backs-up another salesperson." - What is the name of this model? - One-to-one unary relationship Describe the ER model for "(L to R) A salesperson manages zero to many other salespersons." and "(R to L) A salesperson is managed by exactly one other salesperson." - What is the name of this model? - One-to-many unary relationship Describe the ER model for "(L to R) A product can be part of no other products or part of several other products." and "(R to L) A product can be composed of no other products or be composed of several other products." - What is the name of this model? - Many-to-many unary relationship What does 'refer' in Referential Integrity imply? - Referential integrity revolves around the circumstance of trying to refer to data in one relation in the database, based on values in another relation. Define the delete rule RESTRICT... - If the delete rule between two relations is RESTRICT and an attempt is made to delete a record on the "one side" of the one-to-many relationship, the system will forbid the delete to take place if there are any matching foreign key values in the relation on the "many side". Define the delete rule CASCADE... - If the delete rule between two relations is CASCADE and an attempt is made to delete a record on the "one side" of the relationship, not only will the record be deleted but all of the records on the "many side" of the relationship that have a matching foreign key value will also be deleted. - In other words, the delete will "cascade" from one relation to the other. Define the delete rule SET-TO-NULL... - If the delete rule between the two relations is SET-TO-NULL and an attempt is made to delete a record on the "one side" of the one-to-many relationship, that record will be deleted and the matching foreign key values in the records on the "many side" of the relationship will be set to null. Which entity is uniquely identified by concatenating the primary keys of the two entities it connects? Associative entity Candidate Key - If a relation has more than one attribute or minimum group of attributes that represents a way of uniquely identifying the entities, then they are each called a candidate key. Concurrency Problem - When two or more users are trying to update the same record simultaneously. Equijoin Combines two or more tables based on a column that is common to the tables. Foreign Key - When an attribute or group of attributes serves as the primary key of one relation and also appears in another relation. Natural Join - Matches each row in a table against each row in another table based on common values found in columns sharing a common name and data type. Tuple - Rows are referred to as tuples. * in the SELECT clause - It indicates that all attributes of the selected row are to be retrieved AND operator - It displays a record if more than one condition is true AVG() function - It returns the average value of a numeric column. BETWEEN operator - It allows you to specify a range of numeric values in a search. DISTINCT operator - It is used to eliminate duplicate rows in a query result. IN operator - It allows you to specify a list of character strings to be included in a search JOIN clause - It is used to combine rows from more than one table, based on a common field between them. LIKE operator - It allows you to specify partial character strings in a "wildcard" sense. OR operator - It displays a record it either the first condition OR the second condition is true. ORDER BY clause - It simply takes the result of a SQL query and orders them by one or more specified attributes. SELECT command - Data retrieval in SQL is accomplished with the SELECT command. Subquery - When on SELECT statement is "nested" within another in a format, it is known as subquery. Common DDL commands: - CREATE - ALTER - DROP - TRUNCATE - RENAME Common DML commands: - SELECT - INSERT - UPDATE - DELETE - MERGE Write the basic SQL query command: SELECTcolumns FROMtable WHEREpredicates identifying rows to be included Write the SQL query to "Find the commission percentage and year of hire of salesperson 186": SELECT COMMPERCT, YEARHIRE FROM SALESPERSON WHERE SPNUM=186; Write the SQL query to "Retrieve the entire record for salesperson 186": 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.": SELECT SPNUM, SPNAME FROM SALESPERSON WHERE COMMPERCT=10; Write the SQL query to "List the salesperson numbers, salesperson names, and commission percentages of the salespersons whose commission percentage is less than 12.": SELECT SPNUM, SPNAME, COMMPERCT FROM SALESPERSON WHERE COMMPERCT12; Write the SQL query to "List the customer numbers and headquarters cities of all customers that have a customer number of at least 1700": SELECT CUSTNUM, HQCITY FROM CUSTOMER WHERE CUSTNUM=1700; Write the SQL query to "List the customer numbers, customer names, and headquarters cities of the customers that are headquartered in New York and that have a customer number higher than 1500": SELECT CUSTNUM, CUSTNAME, HQCITY FROM CUSTOMER WHERE HQCITY='New York' AND CUSTNUM1500;