SQL query to find duplicate rows, in any table

Question

I\'m looking for a schema-independent query. That is, if I have a users table or a purchases table, the query should be equally capable of catchin

Answer 1

I'm still confused about what "detecting them might be" but I'll give it a shot.

Excluding them is easy

e.g.

SELECT DISTINCT * FROM USERS

However if you wanted to only include them and a duplicate is all the fields than you have to do

SELECT 
   [Each and every field]
FROM
   USERS
GROUP BY
   [Each and every field]
HAVING COUNT(*) > 1  

You can't get away with just using (*) because you can't GROUP BY * so this requirement from your comments is difficult

a schema-independent means I don't want to specify all of the columns in the query

Unless that is you want to use dynamic SQL and read the columns from sys.columns or information_schema.columns

For example

DECLARE @colunns nvarchar(max)
SET  @colunns = ''

SELECT @colunns = @colunns  + '[' +  COLUMN_NAME  +'], ' 
FROM INFORMATION_SCHEMA.columns  
WHERE table_name = 'USERS'

SET  @colunns  = left(@colunns,len(@colunns ) - 1)


DECLARE @SQL nvarchar(max)
SET @SQL = 'SELECT '  + @colunns 
          + 'FROM  USERS' + 'GROUP BY ' 
          + @colunns 
           + ' Having Count(*) > 1'


exec sp_executesql @SQL

Please note you should read this The Curse and Blessings of Dynamic SQL if you haven't already