RDBMS is one of the most popular databases, and this skill is crucial for many job roles. This RDBMS Interview Questions article will introduce you to the most frequently asked questions on RDBMS and the best ways to respond. This serves as a one-stop resource for your interview preparation.
An RDBMS (Relational Database Management System) provides a foundation for numerous applications and services. Top companies widely use relational databases to manage their data. Hence, being well-versed in this technology allows you to remain relevant in the industry.
The following RDBMS Interview Questions are categorized based on their difficulty level: basic, intermediate, and advanced. They address various RDBMS-related topics from all angles and tough questions for experienced RDBMS applicants.
A database management system is a computerized data-keeping system for storing, retrieving, and managing data. A DBMS makes it easy for users to create, read, protect, delete, and update the data in a database.
It serves as an interface between the users and databases, ensuring consistent data access.
The most popular DBMS in enterprise database systems is RDBMS. The complete form is Relational Database Management System.
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Relational database management is a set of programs and capabilities used to create, update, administer, and interact with a relational database among IT teams. A relational database stores and provides access to data points related to one another.
In RDBMS, data storage is in the form of tables, and each row within the table is a record with a unique ID called a key. The table's columns hold the data attributes, and the record usually contains the value of each attribute, to establish the relationship among data points quickly.
Let's take an example of a digital storefront, and understand more clearly how we can structure data in RDBMS.
In the database, we store customer information in tables, with columns representing the names and addresses and rows holding individual customer data.
We can even link or relate the tables using keys. Each row is defined in a table using a unique "Primary Key." The primary key added to another table is referred to as a "Foreign Key." The relationships among the primary/foreign keys form the basis of how relational databases work.
The following structures exist in relational databases
A database is a logical grouping of data. It contains the data associated with one application or with a group of related applications. It includes a collection of related table spaces and index spaces.
A table is a logical structure made of columns and rows. Rows have no specific order, but columns follow a fixed order to retrieve the data.
An index is nothing more than an ordered set of pointers to rows of a table. Unlike the rows of the table, the rows in the indexes maintain a specific order to retrieve data.
A key is one or more columns specified as keys when a table, index, or referential integrity is defined. The various types of keys in RDBMS include primary key, unique key, and foreign key.
There are three main types of relationships between the tables to ensure the absolute flexibility of the relational database model.
Suppose a single record of table A is related to a single record of table B. In that case, it is a one-to-one relationship.
Suppose a single record of table A is related to multiple records of table B. In that case, it is a one-to-many relationship.
Suppose multiple records of table A are related to multiple records of table B. In that case, it is a many-to-many relationship.
The following are the features of RDBMS
Relational databases store data in an easily understandable table format.
Allows multi-user access along with the benefits that let administrators have complete control over databases and provide different levels of access to other users.
Relational databases provide complete ACID support. The term "ACID" means Atomicity, Consistency, Isolation, and Durability, a well-known database property guaranteeing data validity despite errors, failures, and other possible mishaps.
A database management system supports the development and administration of database platforms. An RDBMS is an advanced version of a DBMS that saves data in a row-based table structure. The file storage used in RDBMS is different than DBMS.
Check out the table below to learn more about RDBMS vs DBMS
|Users allowed||Allows one user at a time||Multiple users at a time|
|Amount of Data||Handles a small amount of data.||Takes any amount of data|
|ACID Implementation||Doesn't Support||Supports|
|Database Normalization||DBMS cannot be normalized||RDBMS can be normalized|
|Data redundancy||Common in this model||Doesn't allow|
|Requirements||Less software and hardware||High software and hardware|
|Storage||File storage||Tabular structure|
|Distributed database||DBMS will not support||RDBMS provides complete support|
|Database structure||The hierarchical arrangement of data||Stores data in the form of rows and columns within tables.|
|Security||Lack of security||Good data security due to several log files.|
The RDBMS supports a variety of relational operations, such as
No. OODBMS stands for Object Oriented DataBase Management System. RDBMS is a relational database management system that stores the data as entities.
Specific properties are followed before and after each transaction to maintain database consistency. These are called ACID properties.
ACID properties in RDBMS
A table is a set of data elements organized into rows and columns. A single entry into a table is like a row or a record. There are several records in a table, and they can break down into smaller entities known as fields.
In RDBMS, there are two types of tables - master, and transactions. Identifying them during database development helps you understand how the system interacts with the database.
The below table helps us to decide whether the table is a master or transaction.
|Changes||Data is likely to stay the same.||Data that often changes.|
|Timestamps||It may not require a timestamp with each entry.||Every transaction is usually associated with a timestamp.|
|Records||Less compared to the transaction table.||Records are more.|
|Partitions||Vertical partitioning for normalization.||Horizontal partitioning for easier querying.|
|Use||It stores system information.||It captures system events.|
RDBMS is the optimal choice for data management in every business domain. Examples of popular relational database management systems include MySQL, Oracle, SQLite, SQL Server, PostgreSQL, and Microsoft SQL Server.
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RDBMS is a database management system. Whereas SQL is the language used to communicate with data in an RDBMS.
SQL stands for Structured Query Language. SQL lets you access the data stored within relational databases. Using SQL statements, you can store, update, remove, search, and retrieve data from the database. You can even use it to optimize and maintain the performance of the databases.
Here are the major components of the RDBMS
A table is a collection of tuples or records comprising the values related to the attributes or columns in a table.
In the database, data storage is in the form of various tuples, known as rows, under the attributes. The tuple, record, and row items are stored interchangeably here.
Columns are commonly known as attributes. You can effectively map data using columns.
The domain of a database is the permitted value that a database can store.
A table's structure is known as its schema. The database schema comprises the columns and types of data they hold.
These rules will apply to our data as it is added to and kept up in our database. We maintain our data's accuracy and integrity by using constraints. Depending on the use case, we may have limitations at the column or table level.
Knowing the difference between a NULL value and other values, such as zero or fields with spaces, is crucial. In a table, a NULL value is in a field with no value. During the construction of a record, a field with a NULL value indicates that it was left empty.
The rules enforced on data columns in a table are known as SQL constraints. These limit the kind of information entered in the tables. As a result, the database's data is reliable and accurate.
Both column-level and table-level constraints are possible. Table-level constraints are applied to the entire table, whereas column-level constraints are to just one column.
Some of the most popular SQL constraints are listed below.
|NOT NULL||Stop the column from taking NULL values.|
|DEFAULT||Provides a default value for the column when none is specified.|
|UNIQUE||Ensure that all the values are different in the column.|
|PRIMARY KEY||Uniquely identifies each record in a database table.|
|FOREIGN KEY||Uniquely identifies each record in another database table.|
|CHECK||Ensure that all the values in a column satisfy specific conditions.|
|INDEX||Helps to create and retrieve records fast.|
Data integrity refers to the complete consistency, completeness, and accuracy of data across its entire lifecycle. When data has integrity, mechanisms have been established to ensure that an unauthorized person or software cannot alter data-in-use, data-in-transit, and data-at-rest.
The major types of Data Integrity in an RDBMS are as follows
|Entity Integrity||This one states that a table cannot include any duplicate tuples.|
|Domain Integrity||This one directs us to save data in any specified column in the proper format, type, and range.|
|Referential Integrity||This one states that we cannot delete necessary records for accessing other records.|
|User-Defined Integrity||This one states that the rules given by the user when creating the database are consistently applied and verified before entering data into the database.|
Database Normalization is a process used to filter and organize data in a database. Normalization helps you to do the following:
Eliminates redundant data, thus permitting practical usage of available memory.
Ensures the data dependencies' logical consistency.
There are four primary normal forms that we need to understand
We ensure that no multi-value records exist in a database when it is in the First normal form. For every attribute, there is only one value present in each record.
When a database is in the Second Normal Form state, it must adhere to all the requirements of 1NF. It is not permissible for any columns to depend partially on the primary key.
A database must be in 3NF normal form for it to be in BCNF form. You must also evaluate transitive dependency in addition to this. If the database uses BCNF, there shouldn't be any transitive dependencies.
The following requirements must be satisfied for a database to be in the third normal form
ER Model is an Entity-Relationship Model or high-level data model in RDBMS that represents the entity sets relationship. ER Models are used to outline the database design. By defining entities, attributes, and relationships, ER diagram describes the logical structure of databases.
Any object physically and logically created in the real world is called an entity. Entities are of two types
An attribute is a characteristic or property of an entity. An entity can have numerous attributes.
There are five such attributes
In a DBMS, a relationship primarily refers to the connection between two or more data sets. The datasets can communicate and store data in different tables because of relationships. They also assist in connecting various types of data.
Types of relationships
Data abstraction is the process of hiding unimportant user information. The developers conceal internal, irrelevant customer information to simplify database interaction for customers.
Three levels of abstraction exist
1) Physical: This is the most basic level of abstraction. It explains the storage of memory in records.
2) Logical: The database's current data comprises tables at this level—the relationship between the data items stored in comparatively simple structures.
3) View: The third level of abstraction is a view. The actual database is only partially visible to users.
Indexes are unique RDBMS objects that let users quickly retrieve records from the database.
There are primarily two indexing methods
Cluster indexing is the term used to describe storing more than two records in a single file.
It provides a list of virtual pointers or references to the location where the data is stored, i.e., it does not attempt to cluster the data. Data doesn't follow index order. Instead, leaf nodes include the data.
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In RDBMS, the buffer manager allows relational operators, heap files, and access methods to read, write, allocate, and de-allocate pages. These operations are carried out on disc pages by the underlying DB class object, which the buffer manager invokes.
A database lock is a method that prevents two or more database users from updating a shared piece of data simultaneously. No other database user or session can edit the data once a single database user or session has obtained a lock. This limitation remains in place until the lock is released. There are two different types of locks, namely:
Also known as a Read-only lock. The transaction in the share lock pattern can only read the data item.
The transaction can read and write the data item in the exclusive lock.
|Basis of Comparison||Relational Algebra||Relational Calculus|
|Language||Procedural language||Declarative language|
|Procedure||It means how to obtain the results.||It means what results have to obtain.|
|Order||The order is specified to perform the operations.||Order not specified.|
|Programming language||Nearer to programming languages.||Nearer to natural language|
|Inclusion in SQL||Only a few relational algebraic features are present in SQL.||The tuple relational calculus forms the basis of SQL to a greater extent.|
|Query Evaluation||Query evaluation relies on the specification of the order in which you must perform operations.||The order of operations doesn’t matter for the evaluation of queries.|
The below table illustrates the differences between DELETE and TRUNCATE commands
|Specific rows get deleted using the DELETE command (one or more).||While using this command, all the rows in a table get deleted.|
|It is a DML command (Data Manipulation Language).||It’s a DDL (Data Definition Language) command.|
|The DELETE command could include a "WHERE clause" for records filtering.||While the TRUNCATE command does not include a "WHERE clause."|
|A tuple gets locked before being deleted when using the DELETE command.||The data page is locked while this command runs before the table data gets deleted.|
|The DELETE command eliminates rows one at a time while adding a transaction log entry for each deleted row.||By reallocating the data pages used to store the table data, TRUNCATE Database removes the data from the table. It simply logs the page deallocations in the transaction log.|
|Compared to TRUNCATE, DELETE is the slower command.||The TRUNCATE command, however, is quicker than the DELETE command.|
|You require the table's DELETE permission to utilize Delete.||We require at least the ALTER permission on the table before using Truncate.|
|Using the DELETE Statement on the table leaves the identification of the fewer columns intact.||Identity If an identity column is present in the table, you can reset it to its seed value.|
|This command also has an active trigger option.||This command does not have an active trigger option.|
|Compared to Truncate, the DELETE statement uses more transaction spaces.||Truncate statements take up fewer transaction spaces than DELETE statements.|
The term "extension" refers to the total number of tuples in a table at any time and entirely relies on the time.
Intention does not depend on time and describes the table's name, configuration, and restrictions.
Data independence describes how freely any program can access the information it stores. It is for storage configuration and enables data modification presented in the database. There are two kinds of data independence:
It allows the modification to be made in the physical point and won't affect the logical point.
It makes it possible to finish the modification at the logical level and affects the view level.
Database Management System is known as DBMS, and Relational Database Management System is known as RDBMS. Unlike RDBMS, which stores data in tables, DBMS stores data as a file.
To create, update, and retrieve data in RDBMS, one must utilize the standard database language known as structured query language (SQL).
There are four types of DBMS
The data is stored using parent-child relationships in this DBMS. There are several different hierarchical database management systems.
To make data accessible and usable, they organize it in a way that resembles a tree. Similar to this, the tree's nodes contain the DBMS configuration.
Many-to-many relationships are supported by network DBMS, creating intricate database architectures. RDM Server best exemplifies the network DBMS.
Relational DBMS uses tables, also known as relations or tuples, to store data based on database relationships. They offer many-to-many relationships but only predefined data types.
You can store various data types with this DBMS. It stores data in objects.
A relational database management system comprises several components. Tables, records, attributes, instances, schemas, and keys form a relational database.
RDBMS provides four primary functions as follows −
It is one of the essential RDBMS functions. Rules are established by security management that permit access to the database. Additionally, this function limits the specific data that any user may see or write.
Primary and foreign key concepts are used in relational database management systems to connect several tables. There is no data repetition. As a result, it eliminates the possibility of data duplication. RDBMS accuracy is, therefore, good.
Data integrity enforces the three constraints. Entity integrity means the use of a table's primary key.
The relational model in RDBMS offers the best data consistency for keeping data between application and database copies.
Some examples of RDBMS include Oracle, Microsoft SQLServer, MySQL, and PostgreSQL.
You can create a set of SQL statements that numerous applications can use by creating a trigger since it is stored in the database and is accessible to everyone with the necessary privileges. When multiple programs must carry out the same database operation, you can avoid redundant code by using triggers.
Keeping in mind these tips improve your chances of clearing an RDBMS interview successfully
This brings us to the end of our post on RDBMS interview questions, and there is a high probability that your interviewer will ask these questions. Be thorough with your responses. For more preparation, you can check out our RDBMS Training Courses.
Also, if you have attended an RDBMS interview recently, we urge you to post any new or tough questions you faced. So that our experts will come up with the best possible solution.
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