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Frequently asked SQL interview questions answer

1 - What is SQL and what are its main features?

Answer:
SQL (Structured Query Language) is a domain-specific language used for managing and manipulating relational databases.
Main features of SQL include:

-Data query and retrieval
-Data insertion, update, and deletion
-Schema creation and modification
-Data access control
-Transaction management


2 - Order of writing SQL query?

Answer:
The general order of writing an SQL query is:

1.SELECT
2.FROM
3.WHERE
4.GROUP BY
5.HAVING
6.ORDER BY
7.LIMIT/OFFSET (for databases that support pagination)


3 - Order of execution of SQL query?

Answer:
The order of execution of an SQL query is:

1.FROM clause
2.WHERE clause
3.GROUP BY clause
4.HAVING clause
5.SELECT clause
6.ORDER BY clause


4 - What are some of the most common SQL commands?

Answer:
Some of the most common SQL commands are:

-SELECT: Retrieves data from a database
-INSERT: Adds new data to a database
-UPDATE: Modifies existing data in a database
-DELETE: Removes data from a database
-CREATE: Creates a new database, table, or view
-ALTER: Modifies a database, table, or view structure
-DROP: Deletes a database, table, or view
-JOIN: Combines rows from two or more tables based on a related column


5 - Whatโ€™s a primary key & foreign key?

Answer:

* Primary Key: A primary key is a unique identifier for a record in a table. It ensures that each record in a table is unique and not null.

* Foreign Key: A foreign key is a column or a set of columns in a table that establishes a link between the data in two tables. It establishes a relationship between the two tables and ensures referential integrity.


6 - All types of joins and questions on their outputs?

Answer:
Types of joins in SQL include:

-INNER JOIN: Returns records that have matching values in both tables.
-LEFT JOIN (or LEFT OUTER JOIN): Returns all records from the left table, and the matched records from the right table. If no match, NULL values are returned.

-RIGHT JOIN (or RIGHT OUTER JOIN): Returns all records from the right table, and the matched records from the left table. If no match, NULL values are returned.

-FULL JOIN (or FULL OUTER JOIN): Returns all records when there is a match in either the left or right table. If no match, NULL values are returned.



7 - Explain all window functions and difference between them?

Answer:
Window functions perform calculations across a set of table rows that are related to the current row. Common window functions include:

-ROW_NUMBER(): Assigns a unique sequential integer to rows within a partition of a result set.
-RANK(): Assigns a unique rank to rows within a result set.
-DENSE_RANK(): Similar to RANK() but without gaps in the ranking.
-NTILE(n): Divides the result set into n equally sized groups.
-LEAD(): Provides access to subsequent rows from the current row.
-LAG(): Provides access to previous rows from the current row.


8 - What is stored procedure?

Answer:
A stored procedure is a precompiled collection of one or more SQL statements and control-of-flow statements stored under a name in a database. It can be invoked using a simple call, providing better performance and security, and promoting modular programming.



9 - Difference between stored procedure & Functions in SQL?

Answer:

*Stored Procedure:
Can perform multiple SQL operations.
Can have input and output parameters.
Can't be used in SQL queries.
Can't be used in SELECT statements.
*Function:
Returns a single value.
Accepts only input parameters, doesnโ€™t accept output parameters.
Can be used in SQL queries.
Can be used in SELECT statements.
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๐Ÿš€ 50 JavaScript Interview Questions for 2024 ๐Ÿš€

1.What is JavaScript?
2.What are the data types in JavaScript?
3.What is the difference between null and undefined?
4.Explain the concept of hoisting in JavaScript.
5.What is a closure in JavaScript?
6.What is the difference between โ€œ==โ€ and โ€œ===โ€ operators in JavaScript?
7.Explain the concept of prototypal inheritance in JavaScript.
8.What are the different ways to define a function in JavaScript?
9.How does event delegation work in JavaScript?
10.What is the purpose of the โ€œthisโ€ keyword in JavaScript?
11.What are the different ways to create objects in JavaScript?
12.Explain the concept of callback functions in JavaScript.
13.What is event bubbling and event capturing in JavaScript?
14.What is the purpose of the โ€œbindโ€ method in JavaScript?
15.Explain the concept of AJAX in JavaScript.
16.What is the โ€œtypeofโ€ operator used for?
17.How does JavaScript handle errors and exceptions?
18.Explain the concept of event-driven programming in JavaScript.
19.What is the purpose of the โ€œasyncโ€ and โ€œawaitโ€ keywords in JavaScript?
20.What is the difference between a deep copy and a shallow copy in JavaScript?
21.How does JavaScript handle memory management?
22.Explain the concept of event loop in JavaScript.
23.What is the purpose of the โ€œmapโ€ method in JavaScript?
24.What is a promise in JavaScript?
25.How do you handle errors in promises?
26.Explain the concept of currying in JavaScript.
27.What is the purpose of the โ€œreduceโ€ method in JavaScript?
28.What is the difference between โ€œnullโ€ and โ€œundefinedโ€ in JavaScript?
29.What are the different types of loops in JavaScript?
30.What is the difference between โ€œlet,โ€ โ€œconst,โ€ and โ€œvarโ€ in JavaScript?
31.Explain the concept of event propagation in JavaScript.
32.What are the different ways to manipulate the DOM in JavaScript?
33.What is the purpose of the โ€œlocalStorageโ€ and โ€œsessionStorageโ€ objects?
34.How do you handle asynchronous operations in JavaScript?
35.What is the purpose of the โ€œforEachโ€ method in JavaScript?
36.What are the differences between โ€œletโ€ and โ€œvarโ€ in JavaScript?
37.Explain the concept of memoization in JavaScript.
38.What is the purpose of the โ€œspliceโ€ method in JavaScript arrays?
39.What is a generator function in JavaScript?
40.How does JavaScript handle variable scoping?
41.What is the purpose of the โ€œsplitโ€ method in JavaScript?
42.What is the difference between a deep clone and a shallow clone of an object?
43.Explain the concept of the event delegation pattern.
44.What are the differences between JavaScriptโ€™s โ€œnullโ€ and โ€œundefinedโ€?
45.What is the purpose of the โ€œargumentsโ€ object in JavaScript?
46.What are the different ways to define methods in JavaScript objects?
47.Explain the concept of memoization and its benefits.
48.What is the difference between โ€œsliceโ€ and โ€œspliceโ€ in JavaScript arrays?
49.What is the purpose of the โ€œapplyโ€ and โ€œcallโ€ methods in JavaScript?
50.Explain the concept of the event loop in JavaScript and how it handles asynchronous operations.
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most asked DSA Questions:

Array:
-How is an array sorted using quicksort?
-How do you reverse an array?
-How do you remove duplicates from an array?
-How do you find the 2nd largest number in an unsorted integer array

Linked Lists:
-How do you find the length of a linked list?
-How do you reverse a linked list?
-How do you find the third node from the end?
-How are duplicate nodes removed in an unsorted linked list?

Strings:
-How do you check if a string contains only digits?
-How can a given string be reversed?
-find the first non-repeated character?
-find duplicate characters in strings/

Binary trees:
-How are all leaves of a binary tree printed?
-How do you check if a tree is a binary search tree?
-How is a binary search tree implemented?
-find the lowest common ancestor in binary tree?

Graph:
-How to detect a cycle in a directed graph?
-How to detect a cycle in an undirected graph?
-Find the total number of strongly connected components?
-Find whether a path exists between two nodes of a graph?
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Crack Your SQL Server Interview: 50 Questions Explained & Asked by MANG & FAANG Companies
https://youtu.be/oGhO-6ZB4vw
50_Essential_SQL_Server_Interview_Questions_MANG_&_FAANG_Style.rar
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Crack Your SQL Server Interview: 50 Questions Explained & Asked by MANG & FAANG Companies
https://youtu.be/oGhO-6ZB4vw
Are you preparing for an SQL interview? Here are some essential SQL questions to help you ace your next interview! ๐Ÿ‘จโ€๐Ÿ’ป๐Ÿ“Š
๐Ÿ” Basic SQL Concepts:
๐Ÿ“Œ Explain the difference between SQL and NoSQL databases.
๐Ÿ“Œ What are the common data types in SQL?
๐Ÿ“‹ Querying:
๐Ÿ“Œ How do you retrieve all records from a table named "Customers"?
๐Ÿ“Œ What is the difference between SELECT and SELECT DISTINCT in a query?
๐Ÿ“Œ Explain the purpose of the WHERE clause in SQL queries.
๐Ÿ”— Joins:
๐Ÿ“Œ Describe the types of joins in SQL (INNER JOIN, LEFT JOIN, RIGHT JOIN, FULL JOIN).
๐Ÿ“Œ How would you retrieve data from two tables using an INNER JOIN?
๐Ÿ“Š Aggregate Functions:
๐Ÿ“Œ What are aggregate functions in SQL? Can you name a few?
๐Ÿ“Œ How do you calculate the average, sum, and count of a column in a SQL query?
๐Ÿ” Grouping and Filtering:
๐Ÿ“Œ Explain the GROUP BY clause and its use in SQL.
๐Ÿ“Œ How would you filter the results of an SQL query using the HAVING clause?
๐Ÿ”„ Subqueries:
๐Ÿ“Œ What is a subquery, and when would you use one in SQL?
๐Ÿ“Œ Provide an example of a subquery in an SQL statement.
๐Ÿ”ง Indexes and Optimization:
๐Ÿ“Œ Why are indexes important in a database?
๐Ÿ“Œ How would you optimize a slow-running SQL query?
๐Ÿ“š Normalization and Data Integrity:
๐Ÿ“Œ What is database normalization, and why is it important?
๐Ÿ“Œ How can you enforce data integrity in a SQL database?
โš™๏ธ Transactions:
๐Ÿ“Œ What is a SQL transaction, and why would you use it?
๐Ÿ“Œ Explain the concepts of ACID properties in database transactions.
๐Ÿ“‹ Views and Stored Procedures:
๐Ÿ“Œ What is a database view, and when would you create one?
๐Ÿ“Œ What is a stored procedure, and how does it differ from a regular SQL query?
๐Ÿ”ฅ Advanced SQL:
๐Ÿ“Œ Can you write a recursive SQL query, and when would you use recursion?
๐Ÿ“Œ Explain the concept of window functions in SQL.
๐Ÿ“Œ For more SQL insights and tutorials, follow #coderbaba and stay tuned for more updates! ๐Ÿ’ก
#SQL #SQLServer #Database #InterviewPreparation #Coding #Programming
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