SQL interview question | Challenge yourself | SoftwaretestingbyMKT | Interview Preparation on SQL

Some important SQL Interview Questions
1. What is Data Integrity in SQL?
2. How to Identify Primary and Foreign Key in SQL?
3. What is Normalization in SQL?
4. What are the types of joins in SQL?
5. What is Projection in SQL?
6. WHat is Selections in SQL?
7. What are the types of SQL?
8. What is the Difference between Delete, Drop and Truncate?
9. What is DQL?
10. What is TCL?
11. What is DDL?
12. What is DML?
13. What is DCL?
14. What are Sub queries?
15. What are special operators in SQL?
16. What are logical operators in SQL?
17. What are conditional/relational operators in SQL?
18. What is wild card search
19. How to do Sorting?
20. Explain group by?
21. When having a clause can come in the picture?

Join this channel to get access to perks:

Like, share and subscribe to the channel.
API Testing Playlist

Core Java Playlist

This calling statement in Java or this() video

Constructor Overloading in Java video

Constructor in Java video

Static and Non Static Variables in Java video

How to Create an Object in Java & Handing non Static method video

Multiple static methods inside a single Class | How to deal it?

Methods in Java | What exactly is public static void main(String[] args)

Types of Variables in Java | Local,Global & Final Variables

Variable and Datatype in Java

Easy way to run a program in Java | First program in Java

Class and Object in java

50 Keywords in Java

Tokens in Java

How Java internally works?| Compilation & Interpretation

Introduction to Java | History of Java |Features of Java
Derived model in software development life cycle video link

Prototype model in software development life cycle video link

Spiral model in software development life cycle video link

Verification and Validation in software development life cycle video

Hybrid model in software development life cycle video video

Waterfall model in software development video link

Software development life cycle video link

What is manual testing, it's advantages and disadvantages video link

What is Software testing video link

I work in the IT industry as a Senior Software QA Engineer in Bangalore, India and I have worked on mobile applications, web applications, and API testing.
The main reason behind this channel is to educate people about software testing so that it will helpful for them to choose the right career and also to prepare for their interviews.

Adding my blog link

Adding my personal mail Id:

Adding my Quora profile link here:

Adding my Twitter account here,
or
Facebook Page:

Join us on Telegram today,
SoftwaretestingbyMKT
For the latest update on software jobs and to discuss each and everything about Software Testing also get an opportunity to get on an audio/video call with me directly to you.
I make videos on daily basics and also help student all over the world for FREE. If my videos are helpful in anyway help "SoftwaretestingbyMKT" reach billions by supporting
OR

[professor]

Foreign Key
1. Can be multiple in a table
2. Can hold duplicate value
3. Can hold NULL value
4. Must define the reference table

[sujatanaik]

Yes, foreign key is having null and duplicate value

[deepanshu]

Foreign key can have duplicate values, but it typically cannot have null values. A foreign key is used to establish a link between two tables in a relational database, and it refers to a unique key in another table. Duplicate values are allowed in the foreign key column, as long as each value corresponds to a unique record in the referenced table. However, null values are often not allowed in a foreign key column, as they wouldn't point to any specific record in the referenced table.

[rajeshwariuma]

Yes, it has null and duplicate values
And i have one doubt, if a key want to become a foreign key, it is the primary key for its parent table. Primary key doesn't allow null values and duplicate values, then how foreign key allow duplicate and null values. Can u explain it

[sohanmondali.r.]

FOREIGN KEYS in SQL are used to create a link between two tables. It is a column that creates a relationship between the tables by taking a reference from another table in the same database using the primary key. The foreign key may contain null and duplicate values. ❤❤❤

[sudhakarn]

Foreign key can take null and duplicate values

[shwethargowda]

foreign can have a null & duplicate values but it doesn't contain the values which is not present in the primary key

[sarosilucian]

The foreign key values in a table can be null. The foreign key may contain duplicate values.

[_AnkitaRajput]

Yessss, it accept duplicate and null value in olap system, because in analytic system it's maintain current data and historical data also.

[shivuprakash]

Yes foreign key can have null and duplicate valves and repeated valves. If a column to become a foreign key it should be a primary key in its own table

[tanmaykumar]

Obviously foreign keys can be duplicate and yes it can take null values and the reason is when we use "on delete null".

[jaypoul]

Foreign key can be * consist of null & duplicate values

[somnathwagchoure]

I think no sir,
because primary key constraint should be metioned for 1st table so that we can use it as foreign key in another table.
Primary key of 1 table acts as a foreign key of another table.

[akashjadhav-nmvw]

I have a question, we know that foreign key is reference to the primary key from another table, and we know primary key doesn't have null values then how foreign key is accepting the null values?

[djsouljah]

The behavior of foreign keys in SQL can vary depending on how they are defined. A foreign key's configuration determines whether or not it can contain null or duplicate values.

Null Values:

By default, foreign keys can have NULL values. This means that a column in a table that is a foreign key can be NULL if the corresponding relationship is optional. In other words, it's not required for every row in the referencing table to have a valid reference to the referenced table.

If you want to enforce that a foreign key column cannot have NULL values, you can specify this using the NOT NULL constraint when defining the foreign key.

Duplicate Values:

Foreign keys can have duplicate values, meaning that multiple rows in the referencing table can reference the same row in the referenced table.

For example, if you have a foreign key relationship between an "orders" table and a "customers" table, multiple orders can reference the same customer.

[Ayushk]

Yes, it contains duplicate and null values bcoz it joins two columns, so it can contains null and duplicate.

[sivayaDamaraju]

Yes, foreign key may contain null and Duplicate values.
Foreign key in SQL are used to cya link between two tables

[ikplhlr]

No..foreign keys depends on primary key..primary keys doesn't allow null and duplicate values in it..

[hemantsonkusare]

Yes ofcourse, but primary key table in not allowed

[omeeebandal]

Foreign key can be duplicate or repeated