What are the rules to be applied to nulls whilst doing comparisons?

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what are the different tables present in mysql? : Sql dba

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Why are sql stored procedures used?

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What are triggers in sql?

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how to check the 3rd max salary from an employee table? One of the queries used is as follows: select sal from emp a where 3=(select count(distinct(sal)) from emp b where a.sal<=b.sal). Here in the sub query "select count(distinct(sal)) from emp b where a.sal<=b.sal" or "select count(distinct(sal)) from emp b where a.sal=b.sal" should reveal the same number of rows is in't it? Can any one here please explain me how is this query working perfectly. However, there is another query to get the 3rd highest of salaries of employees that logic I can understand. Pls find the query below. "select min(salary) from emp where salary in(select distinct top 3 salary from emp order by salary desc)" Please explain me how "select sal from emp a where 3=(select count(distinct(sal)) from emp b where a.sal<=b.sal)" works source:http://www.allinterview.com/showanswers/33264.html. Thanks in advance Regards, Karthik.

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Is inner join same as self join?

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What do you mean by stored procedures? How do we use it?

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What is Difference Between delete and Truncate?

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What is the Diff b/w Constraints and Trigeer

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Are pl sql variables case sensitive?

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Is it possible to access the current value in a session before accessing next value?

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How to run pl/sql statements in sql*plus?

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