SQL Interview Questions and Answers for Beginners

SQL Interview Questions and Answers for Beginners | SQL Interview Questions for Freshers | SQL Interview Questions With Answer | SQL Interview Questions 

SQL Interview Questions and Answers for Beginners: SQL is a domain-specific language used to manage data in a database management system. This is especially useful for dealing with structured data. Here we have shared the Latest SQL Interview Questions and Answers. These SQL questions will be helpful to crack any interview/various competitive exams. Practice SQL interview questions which will improve your performance in exams and interviews. Below mentioned SQL interview questions are frequently asked in interviews. So aspirants who want to join Data Base related jobs, please use these SQL interview questions. Both newbies and experienced users can use frequently asked SQL questions with answers.

SQL is considered as the basis of the database management system. Having complete knowledge of SQL and understanding DBMS related interview questions will make it very easy for you to crack. Here we will know the most focused SQL areas in the last year in IT companies and questions about the technology that is currently on the growth path.

SQL Interview Questions and Answers for Beginners

1. What is SQL?

Structured query language (SQL) is a programming language for storing and processing information in a relational database.

2. What are SQL dialects? Give some examples.

PostgreSQL, MySQL, Oracle, and SQL Server are all database products by different vendors. SQL is the programming language used to talk to these databases, and each database product has its own variant of SQL. We call these variants SQL dialects.

3. What are the main applications of SQL?

PostgreSQL, MySQL, Oracle, and SQL Server are all database products by different vendors. SQL is the programming language used to talk to these databases, and each database product has its own variant of SQL. We call these variants SQL dialects.

4. What types of SQL commands (in SQL subsets) do you know?

Based on functionalities performed by them, there are five types of SQL Commands:

1. DDL(Data Definition Language),

2. DML(Data Manipulation Language),

3. DQL(Data Query Language),

4. TCL(Transaction Control Language),

5. DCL(Data Control Language).

5. Give some examples of common SQL commands of each type.

DDL: CREATE, ALTER TABLE, DROP, TRUNCATE, and ADD COLUMN
DML: UPDATE, DELETE, and INSERT
DCL: GRANT and REVOKE
DCL: COMMIT, SET TRANSACTION, ROLLBACK, and SAVEPOINT
DML: SELECT

6. What is DBMS?

A Database Management System (DBMS) is a program that controls the creation, maintenance, and use of a database. DBMS can be termed as a File Manager that manages data in a database rather than saving it in file systems

7. What is RDBMS?

RDBMS stands for Relational Database Management System. RDBMS stores the data in the collection of tables, which are related by common fields between the columns of the table. It also provides relational operators to manipulate the data stored in the tables. Example: SQL Server.

8. What is a Database?

The database is nothing but an organized form of data for easy access, storing, retrieval and managing of data. This is also known as a structured form of data which can be accessed in many ways. Example: School Management Database, Bank Management Database.

9. What are tables and Fields?

A table is a set of data that are organized in a model with Columns and Rows. Columns can be categorized as vertical, and Rows are horizontal. A table has specified a number of columns called fields but can have any number of rows which is called a record.

10. What is a unique key?

A Unique key constraint uniquely identified each record in the database. This provides uniqueness for the column or set of columns. A Primary key constraint has an automatic unique constraint defined on it. But not, in the case of Unique Key. There can be many unique constraints defined per table, but only one Primary key constraint is defined per table.

11. What is a join?

This is a keyword used to query data from more tables based on the relationship between the fields of the tables. Keys play a major role when JOINs are used

12. Which operator is used in a query for pattern matching?

LIKE operator is used for pattern matching, and it can be used as,
1. % – Matches zero or more characters.
2. _(Underscore) – Matching exactly one character

13. What is the command used to fetch first 5 characters of the string?

There are many ways to fetch first 5 characters of the string -.
Select SUBSTRING(StudentName,1,5) as studentname from student Select RIGHT(Studentname,5) as studentname from student

14. How to select unique records from a table?

Select unique records from a table by using DISTINCT keyword.
Select DISTINCT StudentID, StudentName from Student.

15. How to fetch common records from two tables?

Common records result set can be achieved by,
Select studentID from student. <Strong> INTERSECT </Strong> Select StudentID from Exam

16. How can you create an empty table from an existing table?

Select * into studentcopy from student where 1=2
Here, we are copying student table to another table with the same structure with no rows copied.

17. How to fetch alternate records from a table?

Records can be fetched for both Odd and Even row numbers:
To display even numbers-.
Select studentId from (Select rowno, studentId from student) where mod(rowno,2)=0
To display odd numbers-.
Select studentId from (Select rowno, studentId from student) where mod(rowno,2)=1
from (Select rowno, studentId from student) where mod(rowno,2)=1.[/sql]

18. What is the difference between TRUNCATE and DROP statements?

TRUNCATE removes all the rows from the table, and it cannot be rolled back. DROP command removes a table from the database and operation cannot be rolled back.

19. What is Union, minus and Interact commands?

UNION operator is used to combine the results of two tables, and it eliminates duplicate rows from the tables.
MINUS operator is used to return rows from the first query but not from the second query. Matching records of first and second query and other rows from the first query will be displayed as a result set.
INTERSECT operator is used to return rows returned by both the queries.

20. What is CLAUSE?

SQL clause is defined to limit the result set by providing condition to the query. This usually filters some rows from the whole set of records. Example – Query that has WHERE condition Query that has HAVING condition.

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