SQL Interview Questions
Here are some SQL interview questionsthatcoverthe most common SQL interview questions To help prepare you for an SQL interview. This will also cover some partsof SQlscenario-based interview questions which give you a better understanding and help you crack the interview.Then why to wait let’s check out the top interview questions in SQL
1.What is SQL?
SQL, or structured query language, is a crucial tool for extracting relevant and useful data from large datasets. It is a language used to communicate with databases and extract data for application development and data analytics.
2.Define the purpose of SQL?
The purpose of SQL is to manage and manipulate databases, enabling users to perform operations like insert, update, modify, and delete in the database. It is a powerful tool for businesses handling databases, providing insights and flexibility by using simple English words in queries.
3.List out the four types of SQL commands?
The four types of SQL commands are:
Data Definition Language (DDL)
Data Manipulation Language (DML)
Data Control Language (DCL)
Transaction Control Language (TCL)
4.Give the advantages of SQL?
The advantages of SQL include:
High speed
Fast equity processing
Open source availability
Portability
Multiple views of content stored in the database
Efficient in retrieving vast amounts of data using simple queries
Portable
5.Mention the sectors make use of SQL?
SQL is used in various sectors, including:
Education
Healthcare
Retail and e-commerce
Banking and finance
Small companies and startups
6. Define what is a database management system (DBMS)?
A database management system (DBMS) is a software that manages information stored in databases effectively, making it crucial for organizations to ensure data availability to users whenever and wherever needed.
7.What is DBMS architecture?
DBMS architecture helps understand the components of the database systems and their relationships among them. DBMS architecture has three levels:
Physical schema
Logical schema
External schema
8.List out the SQL operators?
SQL operators are reserved words or special characters used to query a database, allowing for data manipulation and performing complex mathematical operations like arithmetic and binary.
9.What are the three types of SQL operators?
The three types of SQL operators are arithmetic operators, subraction operators, and multiplication operators.
10.Mention the function of SQL operators?
SQL operators are used to perform various tasks, including adding values to numerical data, subtracting numerical data, multiplying numerical values of two or more columns of the same table, and dividing numerical values by another column.
11.Point out the difference between SQL and MySQL?
SQL is a programming language with a specific syntax in English words, while MySQL is an RDBMS (Relational Database Management System) used for querying relational database systems. SQL Server is a licensed product of Microsoft, while MySQL is an open-source platform managed by Oracle Corporation.
12.What is the purpose of keys in SQL?
Keys in SQL are attributes or self attributes that help identify rows at tables and establish relationships between multiple tables in the databases. They uniquely identify each record using certain columns, making them essential for large data sets. Keys also allow users to establish identifier relationships between tables and access or manage the store directly.
13.list the different types of keys in SQL?
There are four types of keys in SQL: primary keys, super keys, candidate keys, and foreign keys.
14.Define a sub query in SQL?
A sub query in SQL is a type of query that is written inside another query or becomes part of an algebra query. It provides data to the main query or contained query, and is executed once before its parent or outer query.
15.Mention the four types of joins in SQL?
The four types of joins in SQL are inner, outer, left, and right.
16.Give the use of alias in SQL?
Alias is a temporary name given to a table or column during a query, making it more readable and preferred for many queries written for a table.
17.What is the open database method in WebSQL?
The open database method in WebSQL creates a database object using the existing database or creates a new one. It accepts five parameters: database name, version number, text description, size, and creation callback.
18.Tell about the transaction callback in WebSQL?
The transaction callback in WebSQL is used to create a new table named author with unique columns. The primary key and keyword unique are provided to uniquely identify each record.
19.Give definition of execute SQL method in WebSQL?
The execute SQL method in WebSQL can take up to three arguments: transaction callback, error callback, and success callback. It executes read and write operations to perform the result of the query.
20.What is the cast function in WebSQL?
The cast function in WebSQL is a commonly used conversion function that allows users to convert from one data type to another. It is useful for converting results from various data types and performing calculations on two different data types.
21.Define convert function in WebSQL?
The convert function in WebSQL is similar to the cast function but has a more complex syntax. It specifies the format and data type, which is useful for converting strings to date formats.
22.Tell about the cache function in WebSQL?
The cache function in WebSQL is an A and S standard function that is applicable to most SQL Server databases like PostView SQL, MySQL, MariaDB, and MongoDB. It is more portable and less powerful than the convert function, which is generally considered more flexible.
23.List out the difference between the cast and convert functions in WebSQL?
The cast function is used when working with multiple relational databases and has a standardized syntax. It can be used in any database, but the style is optional and limited to certain databases like SQL Server. The convert function specifies the format and data type, which is useful for converting strings to date formats.
24.Define CAST function in MySQL workbench?
To execute the CAST function in MySQL workbench, use the following query: select cast, specify the parameter as sign, and execute the statement. The output will be in the form of the specified data type.
25.Mention what is Convert function in MySQL workbench?
To execute the Convert function in MySQL workbench, use the following query: select convert, specify the parameter as sign, and execute the statement. The output will be in the form of the specified data type.
26.How can sub queries be used with comparison operators in SQL?
Sub queries can be used with comparison operators in SQL to execute a query dependent on the outcome of another query, allowing users to fetch results without writing to distant queries and saving time.
27.What is the difference between a sub query and a join in SQL?
A sub query is a type of SQL query that is added within the where clause of another SQL statement, while a join is a type of SQL query that combines rows from two or more tables based on a common column.
28.How is the WHERE clause used with SQL operators?
A WHERE clause is used with SQL operators to define a condition in SQL.
29.Define stored procedure in SQL?
A stored procedure in SQL is a set of SQL statements that are saved in the database and can be executed by the user.
30.What is a transaction in SQL?
A transaction in SQL is a block of SQL queries or statements executed on data stored in a database management system.
SQL Training
The commit command in SQL is used to save all changes made by a transaction in the database.
32. Give definition of group by in SQL?
SQL group by is a tool that helps users group identical rows in a data table by using a split apply combined technique.
33.What is SQL order by?
SQL order by is a tool in SQL that sorts data in both ascending and descending order.
34.Give the difference between SQL group by and SQL order by?
In group by, attributes under aggregate functions cannot be in the group by clause, while in order by, attributes under aggregate functions can be in the order by clause.
35.Tell how to execute SQL group by and SQL order by statements?
To execute both SQL statements, import the data set of an employee from Google and use the table data import wizard to import the data set. Then, use the direct statement, select star from employees one, to display the records in the table section.
36.Tell about the between operator in SQL?
The between operator is a SQL statement used to test if an expression is within a range of values. It is inclusive, including only the start and end values of the range.
37.What is the purpose of the “create database” keyword?
The purpose of the “create database” keyword is to create a new database in the database system.
38.Can the between operator be used with date values in SQL?
Yes, the between operator can be used with date values in SQL, but the date should be enclosed in single inverted commas to avoid syntax errors.
39.Define the function of DCL?
DCL is responsible for maintaining security, using control access and permissions of database commands.
40.What is the difference between the where clause and having clause in SQL?
The where clause filters individual rows based on specific conditions, while the having clause filters groups instead of one row at a time.
41.Can the where clause and having clause be used together in a SQL query?
Yes, the where clause and having clause can be used together in a SQL query by placing the where clause before the group by statement.
42.How can the between operator be used with the add column operation in SQL?
The between operator can be used with the add column operation in SQL to select rows where a column falls within a specified range of values.
43.Define the use of between operator with the drop column operation in SQL?
The between operator cannot be used with the drop column operation in SQL as it is used to select rows.
44.Define SQL Inner Join?
SQL Inner Join is a type of SQL join used to join two tables based on a common column and select records with matching values in these columns.
45.What is SQL Left Join?
SQL Left Join is a type of SQL join used to return all records from the left table and matching records from the right table.
46.Give definition of SQL Right Join?
SQL Right Join is a type of SQL join used to return all records from the right table and matching records from the left table.
47.Tell about SQL Cross Join?
SQL Cross Join is a type of SQL join used to return all possible combinations of records from two or more tables.
48.What are SQL keys?
SQL keys are crucial in relational databases for identifying unique rows from tables. They are a subset of simple and simple and simple, and are used to manage large amounts of information stored across multiple tables.
49.Point the difference between primary key and candidate key?
The primary key is a subset of candidate keys that uniquely identify each row in a table and enforce uniqueness by not accepting duplicate values. A candidate key is a set of one or more columns that uniquely identify a record in a table.
50.What is the use of super keys?
Super keys are a combination of all possible attributes that can uniquely identify rows or tuples in a table. They are a superset of primary, candidate, and alternate keys, with additional attributes not needed for unique identification.
51.Point out the difference between alternate key and foreign key?
Alternate keys are subsets of candidate keys that can uniquely identify tuples in a table that are not chosen as a primary key. Foreign keys are a column or combination of columns used to establish and force a link between data in two tables.
52.What is the use of aggregate functions in SQL?
Aggregate functions are used to perform calculations on multiple rows of a single column and return a single value. They are used with the group by clause in the select statement, which divides the result set into groups of values.
53.Mention the three types of aggregate functions in SQL?
The three types of aggregate functions in SQL are count, average, and maximum.
54.What is the difference between count and sum functions in SQL?
The count function returns the number of rows satisfying the criteria specified in the number of rows or non-null column values, while the sum function returns the total summation of a specified column value.
55.Mention the difference between average and maximum functions in SQL?
The average function calculates the average value of columns of numeric types, returning the average of all null values, while the maximum function finds the maximum value or highest value of a certain column or expression.
56.What is the difference between a SQL query and a database design process?
A SQL query is used to retrieve data from a database based on specified criteria, while the database design process is used to ensure the integrity, reliability, and quality of the data stored in a database.
57.What is the purpose of SQL functions?
The purpose of SQL functions is to perform calculations on single or multiple rows of a table, and can be categorized into aggregate functions and scalar functions.
58. Give the difference between aggregate functions and scalar functions?
Aggregate functions return a single value after performing calculations on a group of values, while scalar functions return only a single value from an input value.
59.Give the use of SQL aggregate functions in data analysis?
SQL aggregate functions are useful for finding the lowest and highest prices in a table, calculating the average of all items or records in a particular column, and working with single or multiple rows of a table.
SQL Online Training
SQL functions are used for working with single or multiple rows of a table, while data warehousing is the process of extracting, transforming, and loading data from various sources into a centralized repository for analysis.
61.Give the definition of scalar functions in data analysis?
Scalar functions are essential in data analysis as they convert single or multiple arguments into a single value.
62.What is a relational database management system (RDBMS)?
A relational database management system (RDBMS) is a type of DBMS that stores data in tables, organized in rows and columns. It supports multiple users and can manage and access multiple databases simultaneously. RDBMS is one of the most popular data models in DBMS.
63.Define is a DBMS?
A DBMS (Database Management System) is a type of software that stores and manages large amounts of data.
64. Are there any disadvantages of using a DBMS?
The disadvantages of using a DBMS include the need for space, higher maintenance costs, complexity, speed and performance issues, and increased vulnerability.
65.Mention the fields that use DBMS?
DBMS is used in various fields such as banking, education, finance, healthcare, manufacturing, travel, and e-commerce.
66.What are the steps for installing MySQL on a Windows system?
To install MySQL on a Windows system, follow these steps:
Go to the MySQL official website and click on the download section.
Choose the Windows 86 32-bit and signed installer option.
Open the file and give necessary permissions.
Select the products you want to install, such as MySQL Server, MySQL workbench, and MySQL shell.
Click on the “Custom” option to install the products.
67.What is MySQL workbench and what is its installation process?
MySQL workbench is a graphical user interface for managing MySQL databases. The installation process involves downloading and installing three products from a seed drive. After the installation, the server configuration type is found, and the authentication method is set. A root password is set, which will be used later in the process. The Windows service is chosen, and the system files are configured.
68.Define the scale operators in SQL?
Scale operators in SQL are used to specify conditions in SQL statements. They are classified into five categories: arithmetic, logical, comparison, bitwise, and set.
69.What are SQL commands?
SQL commands are classified into four types: data definition language (DDL), which allows users to define tables and make changes to their structure. Commands include create, altar, drop, and trunk. The syntax of create statements is crucial, as it specifies the table name, columns, and data types. However, it is essential to provide the appropriate data type for the columns, as the computer may not accept mismatches.
70.What is DDL in SQL?
Data definition language (DDL) is used to define tables and make changes to their structure.
71.Mention the syntax of SQL statements?
The syntax of SQL statements is essential for understanding and executing SQL queries. For example, to create a table named “employee”, one can use the “create table space employee” command.
72.Define the “alter table” command in SQL?
The “alter table” command adds a modifier or deletes certain columns from an existing table.
73.What is the “drop table” command in SQL?
The “drop table” command removes all data from a table by deleting records in it.
74.Mention about “truncate table” command in SQL?
The “truncate table” command specifies the table name and values to be truncated.
75.What is DML in SQL?
Data manipulation language (DML) is used to access and manipulate data tables.
76.Define the SQL R clause?
The SQL R clause is used to specify multiple conditions to fetch rows or values that satisfy any of the conditions.
77.What is the SQL Limit statement?
The SQL Limit statement is used to fetch records with a limited number of values.
78.Tell about the SQL AS statement in SQL?
The SQL AS statement in SQL is a keyword used to temporarily rename a column in a table.
79.What is the SQL Insert Multiple Rows statement?
The SQL Insert Multiple Rows statement is a useful tool for inserting multiple rows into a table.
80.Define SQL Update statement?
The SQL Update statement is used to update column values in an existing table.
Overall, any individual working with databases would benefit greatly from learning SQL and possessing a firm grasp of its fundamental principles and uses. By practicing answers toSQL basics for interview andSQL examquestions try to have a good SQL interview practice so, that you may demonstrate your expertise before interviews take place. Good luck with your interview.
SQL Course Price
Harsha Vardhani
Author