How to select all rows which have same value in some column

Question

I am new to sql so please be kind   Assume i must display all the employee ids which have the same phone number Both columns are in the same table   How am i to proceed on this problem inner join or something

User · Answer

How about  SELECT   FROM Employees WHERE PhoneNumber IN       SELECT PhoneNumber     FROM Employees     GROUP BY PhoneNumber     HAVING COUNT Employee ID   gt  1         SQL Fiddle DEMO

User · Answer

SELECT   FROM employees e1  employees e2  WHERE e1 phoneNumber   e2 phoneNumber  AND e1 id    e2 id    Update   for better performance and faster query its good to add e1 before    SELECT e1   FROM employees e1  employees e2  WHERE e1 phoneNumber   e2 phoneNumber  AND e1 id    e2 id

User · Answer

select   from Table1 as t1 where     exists           select           from Table1 as t2          where t2 Phone   t1 Phone and t2 id  lt  gt  t1 id         sql fiddle demo

User · Answer

You can do this without a JOIN   SELECT   FROM  SELECT   COUNT    OVER PARTITION BY phone number  as Phone CT       FROM YourTable        sub WHERE Phone CT  gt  1 ORDER BY phone number  employee ids   Demo   SQL Fiddle

[sql] How to select all rows which have same value in some column

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