Database Concepts: Terms and Definitions
Defining a Tuple
A tuple is a single row in a table in the relational model of a database. It represents a set of related data values, where each value is associated with a column or attribute. For example, in a table of employees, one row (or tuple) might contain the details of one employee.
Explaining the Outer Join Operation
An outer join is a type of join in SQL that returns all the rows from one table and the matching rows from the other table. If there is no match, the result will include NULL values for the non-matching columns. There are three types of outer joins:
- Left Outer Join: Includes all rows from the left table and the matched rows from the right table.
- Right Outer Join: Includes all rows from the right table and the matched rows from the left table.
- Full Outer Join: Includes all rows from both tables, with
NULLs for non-matching rows.
What is Normalization?
Normalization is the process of organizing data in a database to reduce redundancy and improve data integrity. It involves dividing a database into smaller, related tables and defining relationships between them. Normalization is achieved in stages called normal forms (1NF, 2NF, 3NF, BCNF, etc.), each with specific rules.
Defining Deadlock
A deadlock occurs in a database when two or more transactions are waiting for each other to release resources, creating a cycle of dependencies that prevents any of the transactions from proceeding. For example, if Transaction A locks Resource 1 and needs Resource 2, while Transaction B locks Resource 2 and needs Resource 1, a deadlock arises.
Defining Data Mining
Data mining is the process of discovering patterns, trends, and insights in large datasets by using techniques from statistics, machine learning, and database systems. It helps extract useful information for decision-making, such as predicting customer behavior or detecting fraud.
Defining a Super Key
A super key is a set of one or more attributes (columns) in a table that can uniquely identify a tuple (row) in that table. A super key may contain additional attributes that are not necessary for uniqueness. For example, in a table of students, {StudentID} and {StudentID, Name} can both be super keys.
What is a Transaction?
A transaction is a sequence of database operations performed as a single logical unit of work. A transaction must satisfy the ACID properties:
- Atomicity: All operations must complete successfully, or none should be executed.
- Consistency: The database must remain in a valid state before and after the transaction.
- Isolation: Transactions should not interfere with each other.
- Durability: Once a transaction is committed, its effects are permanent.
Two Applications of DBMS
Here are two applications of a Database Management System (DBMS):
- Banking Systems: For managing accounts, transactions, and customer information.
- E-commerce Platforms: For storing and retrieving product details, customer data, and order histories.
Defining BCNF
Boyce-Codd Normal Form (BCNF) is a stricter version of the Third Normal Form (3NF) in database normalization. A relation is in BCNF if, for every non-trivial functional dependency X → Y, X is a super key. BCNF eliminates redundancy and dependency anomalies.
Defining a Domain
A domain is the set of all possible values that an attribute (column) in a table can have. For example, the domain of an attribute “Age” might be all positive integers, while the domain of an attribute “Email” would be all valid email addresses.
Defining a Database System
A database system is an organized collection of data, hardware, software, users, and procedures that work together to store, manage, and retrieve data efficiently. It typically includes a database, a Database Management System (DBMS), and the applications accessing the database.
True or False: “Primary Key cannot be Null”
True: A primary key is used to uniquely identify each row in a table, so it cannot have NULL values. This ensures that every row is uniquely identifiable, which is essential for data integrity.