Frequently asked Database, DBMS and SQL Interview Questions and answers for fresher and Experienced developers covering topics such as Record, Field, Table, Database Transactions, Locks, Normalization, Foreign Key, Primary Key, Constraints, SQL Commands, Pattern Matching, SQL Joins, Views, Stored procedure, Trigger, Cluster and Non cluster Index. These SQL interview questions covers basic and advanced topics.
Q1. What is DBMS ?
Database management system is a collection of programs that enables user to store , retrieve , update and delete information from a database .
Q2. What is RDBMS ?
Relational Database Management system (RDBMS) is a database management system (DBMS) that is based on the relational model . Data from relational database can be accessed or reassembled in many different ways without having to reorganize the database tables . Data from relational database can be accessed using a API , Structured Query Language (SQL)
Q3. What is SQL ?
Structured Query Language(SQL) is a language designed specifically for communicating with databases. SQL is an ANSI (American National Standards Institute) standard .
Q4. What are the different type of SQL’s?
Frequently asked SQL Interview Questions
- Data Definition Language (DDL) is a standard for commands that define the different structures in a database. DDL statements create, modify, and remove database objects such as tables, indexes, and users. Common DDL statements are CREATE, ALTER, and DROP.
- Data Manipulation Language (DML) is used to retrieve, store, modify, delete, insert and update data in database. Examples: SELECT, UPDATE, INSERT statements. DDL is abbreviation of Data Definition Language. It is used to create and modify the structure of database objects in database. DML is used for manipulation of the data itself. Typical operations are Insert,Delete,Update and retrieving the data from the table.
- Data Control Language (DCL) is used to control the visibility of data like granting database access and set privileges to create table etc. DCL is a syntax similar to a computer programming language used to control access to data stored in a database (Authorization). In particular, it is a component of Structured Query Language (SQL). Examples of DCL commands include: GRANT to allow specified users to perform specified tasks.
Q5. What are the Advantages of SQL
- SQL is not a proprietary language used by specific database vendors. Almost every major DBMS supports SQL, so learning this one language will enable programmer to interact with any database like ORACLE, SQL ,MYSQL etc.
- SQL is easy to learn. The statements are all made up of descriptive English words, and there aren’t that many of them.
- SQL is actually a very powerful language and by using its language elements you can perform very complex and sophisticated database operations.
Q6. what is a field in a database ?
A field is an area within a record reserved for a specific piece of data. Examples: Employee Name , Employee ID etc
Q7. What is a Record in a database ?
A record is the collection of values / fields of a specific entity: i.e. a Employee , Salary etc.
Q8. What is a Table in a database ?
A table is a collection of records of a specific type. For example, employee table , salary table etc.
Q9. What is a database transaction?
Database transaction take database from one consistent state to another. At the end of the transaction the system must be in the prior state if transaction fails or the status of the system should reflect the successful completion if the transaction goes through.
Q10. What are properties of a transaction?
Properties of the transaction can be summarized as ACID Properties.
- Atomicity: In this , a transaction consists of many steps. When all the steps in the transaction go completed it get reflected in DB or if any step fails, all the transactions are rolled back.
- Consistency: The database will move from one consistent state to another if the transaction succeeds and remain in the original state if the transaction fails.
- Isolation: Every transaction should operate as if it is the only transaction in the system
- Durability: Once a transaction has completed successfully, the updated rows/records must be available for all other transactions on a permanent basis