Question

I need a Postgresql Query that returns the count of every type of combination of record.

For example, I have a table T with columns A, B, C, D, E and other columns that are not of importance:

Table T
--------------
A | B | C | D | E

The query should return a table R with the values from columns A, B, C, D, and a count for how many times each configuration occurs with the specified E value.

Table R
---------------
A | B | C | D | count

When all of the counts for each record are added together, it should equal the total number of records in the original table.

It seems like a very simple problem, but due to my lack of SQL knowledge, I cannot figure out how to do this.

The only solution I can think of is this:

select a, b, c, d, count(*)
  from T
  where e = 'abc'
  group by a, b, c, d

But when adding the counts up from this query, it is way more than the count of the original table. It seems like count(*) shouldn’t be used, or i’m just totally going about this the wrong way. I’d really appreciate any advice as to how I should go about this. Thank you all.

Answer 1

I figured it out, it was something really stupid. I forgot to specify the where ‘E’ = ‘ABC’ clause in the select count(*) when comparing the count. Thanks anyway for your help guys!