Database Design and ER Diagrams

It should be turned into a new entity or table of its own.

A 1:N relationship is established.

It should be added as a foreign key in the new table.

<p>The wifeid can be included as a foreign key in the Persons table.</p> Signup and view all the answers

<p>The wifeid field should not be included in the Persons table.</p> Signup and view all the answers

<p>Aggregation is an abstraction that treats relationships as higher-level entities.</p> Signup and view all the answers

<p>Primary key attributes should conventionally start with 'TablenameID'.</p> Signup and view all the answers

<p>An entity type becomes a table, with each attribute turning into a column.</p> Signup and view all the answers

<p>A multi-valued attribute is represented by a double-line oval.</p> Signup and view all the answers

<p>The format is 'TableName(Attribute1, Attribute2, ...)' with attributes listed in parentheses.</p> Signup and view all the answers

<p>Special characters and reserved words can lead to errors and confusion in database management.</p> Signup and view all the answers

<p>Composite primary keys can be used but must never be null.</p> Signup and view all the answers

<p>Both are treated as a higher-level entity set for combined representation.</p> Signup and view all the answers

<p>SQL stands for Structured Query Language, and its primary purpose is to access and manipulate databases.</p> Signup and view all the answers

<p>The relational model stores data in tables, which are the fundamental building blocks of the database.</p> Signup and view all the answers

<p>Two operations that can be performed using SQL are retrieving data from a database and updating existing records.</p> Signup and view all the answers

<p>DDL statements are used to define the database structure or schema, including creating and altering database objects.</p> Signup and view all the answers

<p>The DELETE command removes records from a table while preserving the space for those records, whereas TRUNCATE removes all records and the space allocated for them.</p> Signup and view all the answers

<p>Besides querying data, SQL allows for creating new databases, tables, stored procedures, and views.</p> Signup and view all the answers

<p>DCL is used to control access to data in the database, including setting permissions on tables, procedures, and views.</p> Signup and view all the answers

<p>One command in DML is SELECT, which retrieves data from a database based on specified criteria.</p> Signup and view all the answers

<p>To associate each employee with their respective department, allowing for proper organization of data.</p> Signup and view all the answers

<p>An alternate key is a candidate key that is not selected as the primary key but can still uniquely identify records in a table.</p> Signup and view all the answers

<p>A composite key consists of two or more attributes that together uniquely identify a record, while a regular primary key consists of a single attribute.</p> Signup and view all the answers

<p>Yes, a table can have multiple alternate keys if it has more than one candidate key aside from the primary key.</p> Signup and view all the answers

<p>In an employee relation, a composite key might include Emp_ID, Emp_role, and Proj_ID to uniquely identify each employee's assignment in a project.</p> Signup and view all the answers

<p>A foreign key establishes a relationship between two tables, referencing the primary key of another table to ensure data integrity.</p> Signup and view all the answers

<p>Companies use alternate keys to provide additional unique identifiers for records, improving data retrieval and ensuring unique data entry.</p> Signup and view all the answers

<p>A composite key is necessary to uniquely identify each combination of employee roles and projects, preventing data duplication.</p> Signup and view all the answers

<p>The GRANT command is used to give users access privileges to the database.</p> Signup and view all the answers

<p>The REVOKE command withdraws access privileges that were previously granted with the GRANT command.</p> Signup and view all the answers

<p>The COMMIT command saves all work done in a transaction.</p> Signup and view all the answers

<p>A SAVEPOINT identifies a point within a transaction to which you can later roll back.</p> Signup and view all the answers

<p>DML statements are not auto-committed and can be rolled back, while DDL statements are auto-committed.</p> Signup and view all the answers

<p>The basic SQL SELECT statement syntax includes SELECT column list, FROM table name, and optional WHERE, GROUP BY, HAVING, and ORDER BY clauses.</p> Signup and view all the answers

<p>An example is: <code>SELECT Sname, Sno AS Rollno FROM Student</code>.</p> Signup and view all the answers

<p>Mathematical operations can be performed directly in the SELECT statement, such as <code>SELECT Sno, Sname, Eng + Maths AS Total FROM Student</code>.</p> Signup and view all the answers

<p>A trivial functional dependency occurs when the right-hand side is a subset of the left-hand side, while a nontrivial dependency has a right-hand side that is not a subset of the left-hand side.</p> Signup and view all the answers

<p>{S#, P#} → S# is a trivial functional dependency.</p> Signup and view all the answers

<p>Closure refers to the set of all attributes that can be functionally determined by a given set of attributes.</p> Signup and view all the answers

<p>Normalization helps to minimize data redundancy and eliminate anomalies such as insertion, update, and deletion anomalies.</p> Signup and view all the answers

<p>Augmentation states that if A → B holds, then adding attributes to both sides results in AC → BC.</p> Signup and view all the answers

<p>One advantage is the reduction of data redundancy, which increases data integrity and effectiveness.</p> Signup and view all the answers

<p>Decomposition allows a single functional dependency A → BC to be broken down into A → B and A → C.</p> Signup and view all the answers

<p>Transitivity states that if A → B and B → C, then A → C holds true.</p> Signup and view all the answers