Basic doubt in OR operator

Hi All:

I am rourke to SQL开发者_开发百科 and here is my doubt is using OR operator. I have an employee table with 2 records, employeeid column of 1st row value is 1 and 2nd row column value is *. My query has to fetch the row with employeeid column value as 1 otherwise it has to fetch the rows with employeeid as *. Finally the query has to fetch either one set of records i.e. set of records with employeeid as 1 or set of records with employeeid as *.

I have used "Select * from Employee where emp_id = '1' or emp_id = '*';" but the resultset is fetching all rows where employeeid value as 1 and *. I want either one set of records only.

How to do it in SQL? Thanks in advance

Try this:

SELECT * 
    FROM Employee 
 WHERE emp_id = '1' 
 UNION ALL
SELECT * 
    FROM Employee 
 WHERE emp_id = '*' 
        AND NOT EXISTS 
        (
            SELECT 1 
                FROM    Employee 
             WHERE emp_id = '1' 
        )

Select * 
from Employee 
where emp_id = case 
        when exists (select * from Employee where emp_id = '1') 
        then '1' 
        else '*' 
    end

select top 1 * from Employee where emp_id = '1' or emp_id = '*' order by emp_id desc

select * from Employee where emp_id = '1'  OR emp_id IS NOT NULL