Here are some DBMS interview questions to help you succeed in your next job interview and land the position you've always wanted by demonstrating your knowledge and competence. To assist you in scoring for your interview and showcasing your command of the subject, we have compiled a list of the most asked questions and answers for DBMS interviews.
A database management system (DBMS) is a collection of tools that can be used to build and manage a database. DBMS is a suite of applications that makes building and managing databases easier.
Some things to know about DBMS:
In this article, I'll show the most frequently asked DBMS questions to ace your interview. Based on the following sections, we have categorized the interview questions:
A database is a logically structured collection of data that can be easily updated, accessed, and managed. Anything created using the create command is a database object, and databases typically contain sets of tables or objects that include fields and records. The fundamental units of data storage, which provide details about a specific table aspect, are an attribute or a column. DBMS uses user-provided queries to extract data from databases.
A database management system is a group of applications or programs that lets users build and keep databases. DBMS allows it to add, delete, update, and do other things to maintain a database. It also provides a tool or interfaces for doing these things. It is software that lets you store data in a way that is safer and more efficient than a file-based system.
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The database life cycle encompasses the fundamental processes of developing a global schema for a logical database, allocating data across a network, and developing regional schemas for DBMSs.
The DBMS life cycle works on 5 major steps that include:
STEP 1: Requirement Analysis
STEP 2: Logical Design
STEP 3: Physical Design
STEP 4: Implementation
STEP 5: Monitoring, modification and maintenance.
DBMS normalization is the process of making sure that a database has as few duplicates as possible. It also helps eliminate problems with inserting, deleting, and updating.
DBMS denormalization is the process of putting data into a database that is already there.
It is done after normalization so that expensive joins are not needed. It is a common way to improve the performance of a database through database optimization.
A database management system called an (RDBMS) relational database management system that stores data in linked tables and enables users to access that data by querying shared fields between those tables.
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This database design method uses diagrams to discuss the connections between entities representing real-world objects. This method makes it easier for the DBA team to grasp the schema.
DELETE command: With the WHERE clause in place, rows can be removed from the table by using this command. If you use a WHERE clause, only those rows will be removed from the database.
SYNTAX: DELETE FROM table_name WHERE condition;
TRUNCATE command: If you want to clear out an entire table in your database, you'll need to use this command. It's the same as a DELETE command without a WHERE clause. This function deletes all rows from a database table.
SYNTAX: TRUNCATE TABLE table_name;
The primary key is the column in a table that contains information that distinguishes each row from all others. In order for Optim to update, insert, delete or restore data from a database table must have the primary key.
Three types of DBMS architecture are:
There could be a lot of foreign keys on a table. If even one part of the foreign key doesn't work, the whole thing doesn't work.
The value of a foreign key is NULL if any of its parts are null.
Domains are the definitions of data types that resolve to another domain or a simple data type. In the language of relational databases, a domain is the range of acceptable values for an attribute of an entity.
If the system crashes before all the changes are written to the disc, the effect of the transaction should still be present once the DBMS notifies the user that it has been completed successfully.
Durability is the term for this quality. When a transaction is committed to the database, the durability feature ensures that the data is stored in non-volatile memory and unaffected by system failure.
Different DBMS types are explained as follows:
The only way to find content in a traditional file-based system is to scan the entire page because there is no indexing. It takes a long time and moves slowly. The other issue is that files often contain redundant and duplicate data, affecting all of them if you alter one. The disorganized nature of traditional file-based systems makes it more difficult to access data.
Lack of concurrency control is another issue, as a single operation can lock the entire page. On the other hand, multiple operations can run concurrently on the same file in DBMS.
Traditional file-based systems also have issues with security, atomicity, integrity checks, and other issues for which DBMSs have workable solutions.
Some of the advantages of DBMS are
Here are some of the languages that can use in DBMS:
1) DML(Data Manipulation Language): It has the commands needed to change the information in the database.
Example: UPDATE, SELECT, DELETE, INSERT, etc.
2) DDL(Data Definition Language): It has all the commands to set up the database.
Examples: ALTER, CREATE, TRUNCATE, DROP, RENAME, etc.
3) TCL(Transaction Control Language): It has commands to handle the database's transactions.
Example: ROLLBACK, COMMIT, and SAVEPOINT.
4) DCL(Data Control Language): It has the commands to work with the database system's user controls and permissions.
Example: REVOKE and GRANT.
ACID is an acronym for "atomicity," "consistency," "isolation," and "durability" in relational database management systems. These features ensure a safe and sound information exchange process between numerous parties.
Primary keys cannot have NULL values, but unique constraints can. A table can have multiple distinct constraints but only one primary key.
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When referring to the Entity-Relationship model, the abbreviation "E-R model" is commonly used. The inspiration for this model comes straight from the world around us. It defines the entities and relationships between them that are required for the system to function. The entity, an attribute of the entity, a relationship set, and an attribute of the relationship set are the primary objects that an E-R diagram in this context can represent.
Data abstraction refers to the process by which unnecessary information is concealed from users. There are three distinct tiers of data abstraction:
Database transactions consist of a group of related operations that must execute in lockstep with one another.
An index in a database table is a data structure that facilitates fast data retrieval at the expense of increased database write activity and storage requirements. Discs can only store data in sequential order.
In a DBMS, the following types of keys are available.
There are two integrity rules in DBMS:
Query-by-example (QBE) is a graphical method for accessing data in a database using query templates known as skeleton tables. It demonstrates how adding sample values to a query template can be utilized.
Database normalization is the process of arranging a database's attributes so that there is less or no duplicate data (having the same data but in different places).
The following goals are for making things normal.
The HDFS cluster has a single NameNode that manages all of the metadata for the DataNodes. HDFS clusters are vulnerable to having a single point of failure because there is only one NameNode in each cluster. Therefore, the failure of NameNode could cause the systems to become inoperable.
The Checkpoint method permanently saves all system logs to the storage drive after they are deleted from the system.
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There is also the concept of a correlated subquery, which is a subquery that depends on the results of another query. Therefore, correlated subqueries are executed for each row of outer queries. Each child query is run just once for each outer query result row.
Correlated subqueries are queries that are used by the parent statement to perform row-by-row processing. A SELECT, UPDATE, or DELETE statement can serve as the parent statement in this case.
The NULL value is used for any attribute whose status is currently unknown. whereas BLANK stands for an empty String value, and ZERO indicates an integer value of zero.
This is entirely dependent on the objective of the database, as each model possesses its own unique collection of benefits and advantages.
For instance, if you are looking for atomic data, the relational model is the one to use because it provides the best results. When working with text or semi-structured data, the document model is the option that will be most effective for you.
A clause is a type of query element in SQL that allows you to filter or personalize how your data is accessed.
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A cursor object is used by applications to temporarily store query results before processing them individually, row by row. The results of SQL queries are also in the form of data collection.
A database state is a description of the information that is currently stored in a database, whereas a database schema is a description of the overall layout of the database. Both of these descriptions can be found in a database.
Around 2.5 quintillion bytes of data are produced daily in the market today. Therefore, we must analyze this data and produce the necessary results using database management systems (DBMS). Data engineering includes all aspects of designing, building, and transforming data pipelines to make them easier for a data science engineer or big data engineer to use. So, we've listed the most frequently asked DBMS interview questions to help you face your interview and solidify your understanding of the subject.
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Madhuri is a Senior Content Creator at MindMajix. She has written about a range of different topics on various technologies, which include, Splunk, Tensorflow, Selenium, and CEH. She spends most of her time researching on technology, and startups. Connect with her via LinkedIn and Twitter .
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