Correlated Subqueries -- HOw are they used?

• Jacob Pressures

  SSCertifiable

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  April 1, 2011 at 3:40 pm

  #389188

  I still struggle the the idea of a correlated subquery. Partially because once i think i've gotten it, i don't ever use it.

  Are correlated subqueries always used with some type of mathematical function?

• spaghettidba

  SSC Guru

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  April 1, 2011 at 3:47 pm

  #1306704

  No, it's not related to math functions.

  You have a correlated subquery when you select data from a subquery using a where clause that refers to fields in the outer query.

  Example:

  SELECT Name, Salary = (

  SELECT Salary

  FROM Salaries

  WHERE PersonId = Persons.PersonId

  )

  FROM Persons

  WHERE Age > 30

  Sorry for the stupid example, hope you understand it anyway.

  Here, Salaries is correlated to Persons by the clause "WHERE PersonId = Persons.PersonId".

  Hope this helps

  Gianluca

  -- Gianluca Sartori