Question

Consider following table

C1    || C2  || C3  || C4
--------------------------
1     || a   || b   || 1
2     || a   || b   || 4
3     || b   || d   || 2
4     || b   || d   || 2

Question 1: Select all rows in which Column C2 , C3, C4 have equal values e.g. select row 3 and row 4 in above example.

Question 2 : Select all rows in which C4 column has duplicates e.g. C4 has value 2 in row 3 and row 4, so select row 3 and 4.

Answer 1

Question 1 query:

SELECT ta.C1
      ,ta.C2
      ,ta.C3
      ,ta.C4
FROM [TableA] ta
WHERE (SELECT COUNT(*)
       FROM [TableA] ta2
       WHERE ta.C2=ta2.C2
       AND ta.C3=ta2.C3
       AND ta.C4=ta2.C4)>1