Top 25 SQL Server Interview Questions - .NET C#

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This video contains the top 25 interview questions asked from SQL Server topic:
00:00 – Introduction
00.56 – Q1. What is the difference between DBMS and RDBMS?
02:23 – Q2. What is a Constraint is SQL? What are its types.
06:45 – Q3. What is the difference between Primary key and Unique key?
08:36 – Q4. What are Triggers and types of triggers?
13:34 – Q5. What is a View?
16:58 – Q6. What is the difference between Having clause and Where clause?
18:23 – Q7. What is Sub query or Nested query or Inner query in SQL?
19:27 – Q8. What is Auto Increment/ Identity column in SQL Server?
21:12 – Q9. What are Joins in SQL?
21:49 – Q10. What are the types of Joins in SQL Server?
24:23 – Q11. What is Self-Join?
27:06 – Q12. Write a SQL query to fetch all the Employees who are also Managers.
30:22 – Q13. What are Indexes in SQL Server?
31:18 – Q14. What is Clustered index?
33:10 – Q15. What is Non-Clustered index?
34:53 – Q16. What is the difference between Clustered and Non-Clustered index?
36:49 – Q17. How to create Clustered and Non-Clustered index in a table?
38:00 – Q18. In which column you will apply the indexing to optimize this query. “select id, class from student where name=”happy””?
39:47 – Q19. What is the difference between Stored Procedure and Functions (at least 3)?
43:30 – Q20. How to optimize a Stored Procedure or SQL Query?
47:12 – Q21. What is a Cursor? Why to avoid them?
51:46 – Q23. What is CTE in SQL Server?
53:41 – Q24. What is the difference between Delete, Truncate and Drop commands?
57:36 – Q25. How to get the Nth highest salary of an employee?
01:00:49 – (Bonus Question) What are ACID properties?
01:03:07 – (Bonus Question) What are Magic Tables in SQL Server?

[soop]

Need interviewer like you who knows logic is magic. some interviewer patterns makes us to loose confidence who expect bookish answers

[aditijain]

Great Explanation!
I gave an interview just a few days back and all the questions were explained here except for one or two.
Thank you!

[pallavipawankar]

This is a great video for interview purpose. Thanks a lot!

[kesavanmechanical]

Very information and useful for my SQL interviews. Thanks Happy.

[ShreyanshiTimes]

Though i am familiar with SQL server quite few years, still lot of points to learn with your video, really nice content. thanks.!

[Manithan]

Great video. Thanks for sharing! There is a minor correction in the video on Delete vs Truncate. While the Delete can be rolled back Truncate can't be rolled back. The video incorrectly mentions that both can be rolled back.

[rasikasamith]

Thank you a lot for the effort to make this valuable video. Keep it up.

[markippo]

Couple things that catched my eyes. 1) Primary Key always creates a clustered index - no, only if CI dosen't exist, if it does nonclustered unique is created.
2) clustered is faster than nonclustered - it depends on what we're doing. If we searching only for indexed columns or non indexed are included into nonclustered index - they will be performing the same or nonclustered will be faster... Overhead is only when nonclustered index needs take rest of the data from a heap or clustered index...
3) Cross join is also part of sql server logical joins (in documentation at least). Logical joins are a wage topic. Some people will also include any operation that is based on physical joins so semi joins, set operations (union, intersect, except, concatenation as union all), aggregates are also included.
4) Self Joins... Oracle people talk a lot about it... I've never heard this phrase in a sql server community...
5) Drop table could be also rolled back in sql server. Answer to this question: Dml VS ddl. Operation on data itself vs definition of the data. Dml are fully logged, ddl minimal...
6) Nth salary... Order by clause is not allowed in derived tables (subqueries). What if more than one person has the same salary? Use dense_rank
7) Consistency stands for capability of rdbms to be consistent apart from transaction result. So if transaction passes - save the data, if not or was hanged - roll itself back to the former state... It is quite obvious when everything's fine but it's really crucial after server crush... After reboot consistency of every db is checked... It has 3 phases - Analysis (what needs to be committed, what needs to be rolled back) Redo - store committed but not saved transactions. Undo - rollback uncomited transactions that were saved (it's called "dirty pages) - it happens when server operates under memory pressure - data are stored despite they're not committed...
7) Improving performance: 1) look at obvious issues with your query/procedure. Do some stuff. It if helped - you're good to go, if not 2) look at estimated execution plan - apply some indexes etc. 3) look at real execution plan - check if your sp is not victim of parameters sniffing etc.
8) memory consumption isn't so important with cursors... Thier iterative nature is... They're terribly slow compered to set/batch operations. That's why never use cursors unless you need to.

[vidhyadharmote]

Seriously..you have explained very nicely, it's very useful 😊 thank you !

[SatinderSingh-cphn]

Again very nice collection and well explained.. 😇😇

[jyothip]

Hi Sir, Thank you so much for these wonderful videos.

Could you please make a video on How To Return A Value From A Stored Procedure in Sql Server.

[ankitbisht]

I think unique key cols can have multiple null values?

[rathika.m]

Can you please do Video for Azure.. Your videos are really useful for us.. Thank you for your effort

[totoro]

Sir can you do normalisation video with practical examples ? Thank you

[jamunadevi]

Thanks sir..coming Saturday I have interview ..I am watching your videos and preparing . I can easily understand your explanation

[satishdan]

Hello you said Truncate can be rollback, but actually Truncate cannot be rollback. By the way excellent video and appreciate your efforts

[vigneshvk]

Can you please create a video about C# design pattern interview questions

[adilkevin]

What to do if the auto-increment value reaches its limit?. Considering that it's a banking application I don't want to delete the older data how are you going to resolve the issue?

[bhargavisunchu]

Can you do video on .Net core please. nice videos

[kansaascollection]

Difference between table variable and cte