Question

Below is the sample data:

c1   c2   c3   c4   c5
1    a1   a     1     1
2    a2   a     2     1
3    a3   a     3     1
4    a4   a     4     1
5    b1   b     1     1
6    b2   b     2     1
7    b3   b     3     1
8    b4   b     4     1
9    a1   c     3     1 

I want to get the the below details:

c1  c2  c3  c4  c5
1    a1  a   1    1
5    b1  b   1    1
9    a1  c   3    1

C1 is primary key, the criteria is for any given unique(c2) where c4 is the lowest, I want to return the contents(all the 5 columns) of the row.

Answer 1

Try this:

SELECT t1.*
FROM Table1 t1
INNER JOIN
(
  SELECT c3, MIN(c4) c4 
  FROM Table1
  GROUP BY c3
) t2 ON t1.c3 = t2.c3 ANd t1.c4 = t2.c4

SQL Fiddle Demo

Update:¹ In SQL the returned results is a set set(unless you specify an ORDER BY clause, it is a cursor in this case), wherein the order is not guaranteed. This is a standard. You should use an ORDER BY clause if you want to guarantee a specific order. In your case , the results is not guaranteed to be ordered like 1 5 9. Add ORDER BY c1 instead.

The ORDER BY clause might be crucial in some cases, for example, if want to get the top three rows, or the maximum one, in this case you have to specify an ORDER BY clause.

So if you wants to persist a specific order the you have specify an ORDER BY.

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¹ As noted by @Fahim Parker, see the comments below.