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misy 5335 Exam/ 93 Questions with Definitive
Solutions/ 2024-2025.
column - Answer: stores a characteristic common to all rows...A logical group of bytes in a row of a relation or a table. The meaning of a column is the same for every row of the relation, and represents an attribute of a relation. Field - Answer: The central table in a dimensional database. Its attributes are called measures. See also measure. ...(1) A logical group of bytes in a record used with file processing. (2) In the context of the relational model, a synonym for attribute. modification actions - Answer: insert, update, and delete...An action that changes the value of a data item.
Structured Query Language (SQL) - Answer: international standard, emerged as the leading technique for data definition and manipulation. Using SQL, you can? - Answer: reconstruct lists from their underlying tables; you can query for specific data conditions; you can perform computations on data in tables; and you can insert, update, and delete data. What is a Database System? - Answer: a database system has four components: users, the database application, the database management system (DBMS), and the database. Why Use a Database? - Answer: A database is used to help people keep track of things, and the most commonly used type of database is the relational database, although nonrelational databases (which are used extensively in online applications such as Facebook and Twitter) are now also widely used. What are the Problems with Using Lists? - Answer: making changes to this list causes ...modification problems. Modification problem - Answer: A situation that exists when the storing of one row in a table records facts about two themes or the deletion of a row removes facts about two themes, or when a data change must be made in multiple rows for consistency.
.receives requests encoded in SQL and translates those requests into actions on the database .a large, complicated program that is licensed from a software vendor; companies almost never write their own DBMS programs. database application - Answer: .a set of one or more computer programs that serves as an intermediary between the user and the DBMS .read or modify database data by sending SQL statements to the DBMS .present data to users in the format of forms and reports .acquired from software vendors, and they are also frequently written in-house Users - Answer: .employ a database application to keep track of things. .use forms to read, enter, and query data, and they produce reports. database - Answer: a self-describing collection of related records/related tables self-describing - Answer: a description of the structure of the database is contained within the database itself.
Related tables - Answer: Tables in a relational database that are connected by a foreign key column and a referential integrity constraint. Metadata - Answer: Data concerning the structure of data in a database used to describe tables, columns, constraints, indexes, and so forth. Metadata is also stored in a data warehouse to describe its contents. Referential integrity constraint - Answer: A relationship constraint on foreign key values. A referential integrity constraint specifies that the values of a foreign key must be a subset of the values of the primary key to which it refers. Concurrency - Answer: ensures that one user's work does not inappropriately interfere with another user's work Functions of a DBMS - Answer: .Create databases .Create tables .Create supporting structures .Read database data .Modify database data (insert, update, and delete) .Maintain database structures
relation - Answer: A two-dimensional array that contains single-value entries and no duplicate rows. The meaning of the columns is the same in every row. The order of the rows and columns is immaterial. Characteristics of a Relation - Answer: 1. Rows contain data about an entity
- Columns contain data about attributes of the entity
- Cells of the table hold a single value
- All entries in a column are of the same kind
- Each column has a unique name
- The order of the columns is unimportant
- The order of the rows is unimportant
- No two rows may be identical Domain integrity constraint - Answer: Also called a domain constraint, a data constraint that limits data values to a particular set of values. Domain - Answer: (1) The set of all possible values an attribute can have. (2) A description of the format (data type, length) and the semantics (meaning) of an attribute. database schema - Answer: the design on which a database and its associated applications are built. Equivalent Sets of Terms - Answer: Table, Row, Column
File, Record, Field Relation, Tuple, Attribute Candidate keys - Answer: .keys that uniquely identify each row in a relation .can be single-column keys, or they can be composite keys primary key - Answer: the candidate key that is chosen as the key that the DBMS will use to uniquely identify each row in a relation alternate key - Answer: Any "losing" candidate keys entity integrity constraint - Answer: The constraint that the primary key column or columns must have unique values so that each row can be uniquely identified What do you do if a table has no candidate keys? - Answer: define the primary key as the collection of all the columns in the table surrogate key - Answer: a column with a unique, DBMS-assigned identifier that has been added to a table to be the primary key are short and numeric and never change—they are ideal primary keys
Determinant - Answer: One or more attributes that functionally determine another attribute or attributes. Well-formed relation - Answer: A relation in which every determinant is a candidate key. Any relation that is not well-formed should be normalized into two or more relations that are well formed. normalization - Answer: the process of examining relations and modifying them to make them well formed Boyce-Codd Normal Form (BCNF) - Answer: A relation in third normal form in which every determinant is a candidate key. First normal form (1NF) - Answer: Any table that fits the definition of a relation. no repeating groups. multivalued dependencies - Answer: are multiple values of a data item normalization process - Answer: Identify all the candidate keys of the relation. Identify all the functional dependencies in the relation. Examine the determinants of the functional dependencies. If any determinant is not a candidate key, the relation is not well formed. In this case: Place the columns of the functional dependency in a new relation of their own. Make the determinant of the functional dependency the primary key of the new relation.
Leave a copy of the determinant as a foreign key in the original relation. Create a referential integrity constraint between the original relation and the new relation. Repeat step 3 as many times as necessary until every determinant of every relation is a candidate key. Data sublanguage - Answer: A language for defining and processing a database intended to be embedded in programs written in another language—in most cases, a procedural language such as PHP, C#, or Visual Basic. A data sublanguage is an incomplete programming language because it contains only constructs for data definition and processing. American National Standards Institute (ANSI) - Answer: The American standards organization that creates and publishes the SQL standards. Extensible Markup Language (XML) - Answer: A markup language whose tags can be extended by document designers. JavaScript Object Notation (JSON) - Answer: a data structuring format based on (1) documents consisting of name/value pairs and (2) arrays. Values can be simple data values, documents, or arrays. Graphical user interface (GUI) - Answer: A user interface in which the user interacts with the application using icons and other visual cues instead of text- based commands.
NOT NULL constraint - Answer: indicates that a value must be supplied when a new row is created NULL constraint - Answer: indicates that null values are allowed, which means that a row can be created without a value for this column DEFAULT keyword - Answer: can be used to set initial values. VarChar - Answer: a variable-length character data type UNIQUE constraint - Answer: there cannot be any duplicated values CONSTRAINT keyword - Answer: can be used to implement various constraints PRIMARY KEY constraint - Answer: column is labeled as NOT NULL and a CONSTRAINT clause has been added at the end of the table definition AUTO_INCREMENT - Answer: indicates that this is a surrogate key that will start at 1 for the first row created and increase by 1 as each additional row is created. FOREIGN KEY constraints - Answer: define foreign keys and their associated referential integrity constraints
percent sign (%) wildcard character - Answer: represents any sequence of zero or more contiguous, unspecified characters (including spaces) in a specific position in the character string. SQL HAVING clause - Answer: applies conditions to the 'groups' that are formed SQL JOIN keyword - Answer: placed between the table names in the SQL FROM clause, where it replaces the comma that previously separated the two table names SQL ON keyword - Answer: leads into an SQL ON clause, which includes the statement of matching key values that was previously in an SQL WHERE clause SQL inner join - Answer: only displays data from the rows that match based on join conditions SQL equijoin - Answer: a join with a join condition containing an equality operator SQL outer join - Answer: created to avoid inner join problem if a row has a value that does not match the WHERE clause condition, that row will not be included in the join result ON UPDATE phrase - Answer: shows what action should be taken if a value of the primary key changes
