Top 250 SQL Interview Questions and Answers

SQL joining is used to combine rows from two or more tables based on a related column between them.

• SQL joining is used to retrieve data from multiple tables based on a related column.

• Common types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, an...read more

Filter student data from database using specific logics

• Filter students by grade level

• Filter students by gender

• Filter students by attendance record

• Filter students by GPA

• Filter students by extracurricular activities

Procedures in SQL are reusable blocks of code that perform a specific task.

• Procedures are stored in the database and can be called multiple times.

• They can accept input parameters and return output parameters.

• Procedures can contain SQL statements, con...read more

A join query is used to retrieve data from multiple tables by linking them based on a common column.

• Use JOIN keyword to combine tables based on a related column

• Specify the columns to be retrieved using SELECT statement

• Use WHERE clause to specify the ...read more

TCL is not related to SQL. It stands for Tool Command Language and is used for scripting and automation.

• TCL is a scripting language used for automation and testing

• It is not related to SQL, which is a language used for managing relational databases

• TCL...read more

SQL encryption is used to protect sensitive data stored in a database by converting it into unreadable form.

• SQL encryption is used to prevent unauthorized access to sensitive data.

• It converts the data into unreadable form using encryption algorithms....read more

I rate my SQL skills as advanced and my Informatica skills as intermediate.

• Advanced SQL skills include complex queries, stored procedures, and performance tuning.

• Intermediate Informatica skills include ETL development, mapping design, and workflow sc...read more

PL/SQL is better than SQL for complex business logic and procedural programming.

• PL/SQL allows for procedural programming, which is useful for complex business logic.

• PL/SQL has better performance than SQL for large datasets.

• PL/SQL has more advanced fe...read more

Removing duplicates using analytical functions in SQL

• Use the ROW_NUMBER() function to assign a unique number to each row

• Partition the data by the columns that define duplicates

• Order the data by the same columns

• Filter out rows with a row number greate...read more

Performance tuning in SQL involves optimizing queries, indexes, and server settings to improve database performance.

• Identify slow queries using profiling tools

• Optimize queries by rewriting or adding indexes

• Adjust server settings such as memory alloca...read more

RDBMS stands for Relational Database Management System. It is a type of database management system that stores data in a structured format.

• Organizes data into tables with rows and columns

• Uses SQL for querying and managing data

• Enforces relationships b...read more

Hive is a data warehousing tool for Hadoop while SQL is a language used to manage relational databases.

• Hive is used for big data processing while SQL is used for relational databases.

• Hive uses Hadoop Distributed File System (HDFS) while SQL uses trad...read more

Concatenate in SQL is done using the CONCAT function or the + operator.

• Use the CONCAT function to concatenate strings in SQL, for example: SELECT CONCAT(first_name, ' ', last_name) AS full_name FROM employees;

• Alternatively, you can use the + operator...read more

Use SQL query to fetch sales data from database for annual report

• Write a SQL query to select sales data from the database

• Filter the data based on the date range for the annual report

• Aggregate the sales data to calculate total sales for the year

• Consid...read more

Query to create a table

• Use CREATE TABLE statement

• Specify table name and column names with data types

• Add constraints if required

A subquery is a query nested inside another query. It is used to retrieve data from multiple tables or perform complex calculations.

• A subquery is enclosed within parentheses and is usually placed within the WHERE or HAVING clause of the outer query.

• T...read more

ACID property ensures that database transactions are processed reliably.

• ACID stands for Atomicity, Consistency, Isolation, and Durability.

• Atomicity ensures that a transaction is treated as a single unit of work, either all or none of its operations a...read more

Copy command is used to copy files or directories from one location to another.

• The syntax of the copy command is 'copy source destination'

• The source can be a file or a directory

• The destination can be a directory or a new file name

• The /Y flag can be u...read more

Recovery models determine how SQL Server manages transaction log files and provides options for data recovery.

• Full recovery model: Allows for complete data recovery by storing all transactions in the transaction log.

• Simple recovery model: Automatical...read more

Truncating a table removes all data from the table while keeping the structure intact.

• Truncate is a DDL (Data Definition Language) command in SQL.

• It is used to quickly delete all rows from a table.

• Truncate is faster than using the DELETE statement.

• Tr...read more

Merge combines two result sets into one, while Union All combines and includes duplicates.

• Merge is used to combine two result sets into one, eliminating duplicates.

• Union All is used to combine two result sets into one, including duplicates.

• Merge requ...read more

Rank functions in SQL are used to assign a rank to each row within a partition of a result set.

• Rank function assigns a unique rank to each row based on the specified criteria.

• Dense rank function assigns consecutive ranks to rows, with no gaps between...read more

DQL stands for Document Query Language. It is used to query documents in a document-oriented database like MongoDB.

• DQL is used to retrieve documents from a MongoDB database.

• It supports a wide range of query operators and expressions.

• DQL can be used t...read more

There are five aggregate functions in SQL.

• Aggregate functions perform calculations on a set of values and return a single value.

• The five aggregate functions are COUNT, SUM, AVG, MAX, and MIN.

• COUNT returns the number of rows in a table or the number o...read more

Joining data refers to the date on which an employee officially starts working at a new company or branch.

• Joining data is the date when an employee's employment officially begins at a new company or branch.

• It is important for HR and administrative pu...read more

SQL DML commands are used to manipulate data in a database.

• DML stands for Data Manipulation Language

• Common DML commands include INSERT, UPDATE, DELETE

• INSERT is used to add new data to a table

• UPDATE is used to modify existing data in a table

• DELETE is ...read more

Dynamic SQL is a technique to generate SQL statements at runtime based on user input or other conditions.

• Dynamic SQL is used to create flexible and customizable queries.

• It allows for the creation of complex queries with multiple conditions.

• Dynamic SQ...read more