Sometimes you need to know for sure that a column value is only used once in a table. Example: you don’t want to have more then 1 record with a social security number. Or maybe you are searching for a duplicate GUID (which BTW should be globally unique). Browsing by hand is not an option: the table is too large. And also the values to compare are difficult to read.

There is only 1 one way to tell for sure, use SQL:

SELECT * from <tablename> where __guid in (
    SELECT __guid
    FROM <tablename>
    GROUP BY __guid
    HAVING count(__guid) >= 2
)