60 thoughts on “Difference between Subquery, Nested Subquery and Correlated Subquery”

  1. Anonymous

    Good one Bro.. U made it simple to understand

    Keep Going
    -Winkey

    Reply ↓
    1. Anonymous

      Author writes as…."eg of For example, if we want to find the name of the course Admin of the course “Oracle”, then the following subquery will be used:-

      select Firstname+' '+Lastname from student where studentid in (select courseadminid from course where coursename ='Oracle')
      "

      But i say in the above query he is retrieving the name of the student first name + last name and not the coureadmin name.

      Reply ↓
    2. Anonymous

      100's of ppl will browse and try to learn something new. So please before posting something on ur blogs pls correct it, veryify it.As already someone pointed out ur insert statement too. What if a newbie trying to learn something out of this blog. Please Ensure before posting anything.

      Reply ↓
    3. admin Post author

      Hi Anonymous,
      First of all thanks for visiting my blog and spent time in writing the comments as comments motivate me to do more better. Second if you read my article carefully u got to know that, in my article, I store the course admin details also in the student table. So by the query which u mention as
      select Firstname+' '+Lastname from student where studentid in (select courseadminid from course where coursename ='Oracle')
      gives me the name of the COURSE ADMIN NOT ANY STUDENT. if you run that query and article carefully u will know that very well.

      So next time read blog carefully before writing such comments.
      Keep visiting my blog.:-)

      Reply ↓
    4. admin Post author

      Hi Anonymous again,
      Yes, you are right hundreds of people visits my blogs daily and give me valuable comments which motivate me to improve my articles quality better. So before giving wrong comments, reading the articles carefully on not just on my blog but on any blog as UR WRONG COMMENTS WILL GOING TO CONFUSE THE OTHER READERS
      sO Please Ensure before posting ANY COMMENTS THAT YOU READ THE FULL ARTICLES .

      Keep visiting my blog and giving me your valuable comments.

      Reply ↓
    5. Anonymous

      hi thanks for responding
      You still did not catch my point… your firstname + lastname gives you the name same as courseadminname but the value is from the studenttable not from the courseadmindetails.. since both are same u are thinking that it is courseadmin name… your courseadmin table is only in your condition and u r not retrieving anything from. please check once again. if possible remove the firstrow in the courseadmindetails and check

      Reply ↓
  4. Anonymous

    hey thanks it was helpful. if u could add certain exapmles for al kind of joins,it would b great…!!

    thanks and cheers…!!

    Reply ↓
  9. Anonymous

    superb sir.The explanation is very easy to understand.

    Reply ↓
  10. Anonymous

    Hi Sir,
    Could you explain me what is generally top n query in oracle.

    Select e1.emp_id from emp e1 where 2 = ( select count(distinct e2.emp_id) from emp_1 e2 where e1.emp_id = e2.emp_id);

    what does here 2 = stands for, i tried with few examples.When 1= given instead of 2 answer changes..could you please explain me..

    Reply ↓
    1. admin Post author

      Hi
      Thanks for your valuable comments.
      Can you please gives more details of your problem as it will help me in explaining.

      Reply ↓
  11. Anonymous

    thank you sir for the wonderful and easy examples. It was very well explained. Thank you once again.

    Reply ↓
  13. Sumeet Lalvani

    Hey Vivek…. Please correct you Insert query.. 🙁
    this your table structure.

    create table Student (Studentid int identity(1,1), Firstname nvarchar(200), Lastname nvarchar(200),Email nvarchar(100))

    And this your insert query..
    insert into Student values ('Atul','Bajaj', 'atul@abc.com' )

    IF you insert like that … Oracle through the error. bcoz you try to insert the varchar value in INT variable. That not right..

    your insert query should like that..
    INSERT INTO Student
    (Firstname, Lastname,Email)
    VALUES
    ('Atul','Bajaj', 'atul@abc.com');

    In that case Oracle insert the value in exact column. 🙂

    Reply ↓
    1. admin Post author

      Hi Sumeet,
      Many thanks for your post. This article is written for SQL Server and in SQL Server, this code work fine.:-). However ur suggestion is good, from now on wards, I will try to mention the alternate command for Oracle too.:-)

      Reply ↓
    1. admin Post author

      Hi Ashok,
      Thanks for your invaluable comments. I will looking forward to add more sql tips puzzles and Example in near future.

      Reply ↓
  21. rupali

    now i understand wt actualy d difference izzz…………. thnkzzz

    Reply ↓
  23. Anonymous

    simply superb… gr8 article.
    how do i improve my sql skills? any thoughts ? thanks.

    Reply ↓
  25. Anonymous

    It could have been more elaborate. This just a very basic type of explaination. Examples also are not upto the standard.

    Reply ↓
  26. Anonymous

    After completing so many certifications if your explanation stuff is so weak like you have provided. I doubt your dedication to the technology & authentication of the certification candidate. Very poor it shows improper professional development with years of experience

    Reply ↓
    1. admin Post author

      Thanks Anonymous for your comments as its motivate me to improve my article quality. But it is better if you give comments based on my articles not on my certificates as it like that you are more concern about my certificate than my article.
      Also some time it is hard to understand why people hide their identity while criticizing someone as sometimes it put a question mark on the person intention.

      Thanks again
      Vivek

      Reply ↓
  28. Anonymous

    Hello Vivek, juz wondering if the below query can be alternate query for correlated query example.
    select A.Coursename , B.Firstname+' '+B.Lastname as CourseAdminName from A.course AND B.STUDENT where b.studentid=a.courseadminid

    Ajay.

    Reply ↓
  31. Anonymous

    In one Of Interview I hve been asked , What is Co-related Query and how it works internally in oracle.
    Also it has been extended wht is diffrenece between co related query and temp table in SQL query.

    Reply ↓
  32. Anonymous

    an excellent example and I really cleared my doubts very clearly…Keep it Guru..

    Reply ↓
  34. Anonymous

    Hello Sir, you have explained the above aricle very well. Based on the above article I want to ask you that, I want to create a query in which I am comparing a field in two different tables and I want to get the record from the table which is having the higher value after that earlier comparision. I am not able to do this. Waiting for your response.

    Reply ↓
  36. Anonymous

    Hey , Can you please tell me what is difference between sub-query and inline view?

    Reply ↓
  38. mani teja varma

    Does this come under nested query??
    SELECT Name
    FROM AdventureWorks2008R2.Production.Product
    WHERE ListPrice =
    (SELECT ListPrice
    FROM AdventureWorks2008R2.Production.Product
    WHERE Name = 'Chainring Bolts' );

    Reply ↓

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