Question

Here is a sample table that mimics my scenario:

COL_1   COL_2   COL_3   COL_4   LAST_COL
A       P       X       NY      10
A       P       X       NY      11
A       P       Y       NY      12
A       P       Y       NY      13
A       P       X       NY      14
B       Q       X       NY      15
B       Q       Y       NY      16
B       Q       Y       CA      17
B       Q       Y       CA      18

The LAST_COL is a primary key so it will be different every time.

I want to ignore LAST_COL and gather some statistics related to the rest of the 4 columns.

Basically, I have millions of rows in my table, and I want to know which set of COL_1, COL_2, COL_3 and COL_4 are having most number of rows.

So, I want a query which can output me all the unique rows with their count of occurrences.

COL_1   COL_2   COL_3   COL_4   TOTAL
A       P       X       NY      3
A       P       Y       NY      2
B       Q       X       NY      1
B       Q       Y       NY      1
B       Q       Y       CA      2

Thanks to anyone who helps me with this.

*I am using MS SQL, if that would make any difference.

Answer 1

SELECT COL_1, COL_2, COL_3, COL_4, COUNT(*)
FROM MyTable
GROUP BY COL_1, COL_2, COL_3, COL_4

If you ever want to weed out rows that don’t have a duplicate:

SELECT COL_1, COL_2, COL_3, COL_4, COUNT(*)
FROM MyTable
GROUP BY COL_1, COL_2, COL_3, COL_4
HAVING COUNT(*) > 1