How to get the count of a grouped by rows - SQL - mysql

Question

So I have this table
table: "tbl_hash"
------------------------------
| id | hash1 | hash2 | hash3 |
------------------------------
| 1 | a | b | c |
| 2 | a | b | c |
| 3 | a | g | d |
| 4 | a | g | d |
| 5 | a | g | d |
------------------------------
I only want to group them by hash1, hash2, and hash3. count them and only return the count which is higher by 2.
So I have this query to get the values I wanted:
select CONCAT(hash1, hash2, hash3) as hashes, COUNT(*) as count from `tbl_hash` group by hashes having `count` > 2 limit 5
^^ the query above works perfectly..
But what If I wanted to get the data and count for each row? Expected output:
--------------------------------------
| id | hash1 | hash2 | hash3 | count |
--------------------------------------
| 1 | a | b | c | 2 |
| 2 | a | b | c | 2 |
| 3 | a | g | d | 3 |
| 4 | a | g | d | 3 |
| 5 | a | g | d | 3 |
--------------------------------------
I'm also planning on converting those to a query builder using DB::table...

Answer 1

You may join your original table to a subquery which finds the counts for each group:
SELECT t1.*, t2.cnt
FROM tbl_hash t1
INNER JOIN
(
SELECT hash1, hash2, hash3, COUNT(*) AS cnt
FROM tbl_hash
GROUP BY hash1, hash2, hash3
HAVING COUNT(*) > 2
) t2
ON t1.hash1 = t2.hash1 AND
t1.hash2 = t2.hash2 AND
t1.hash3 = t2.hash3;
Note that what I wrote above would completely filter off any original records belonging to a hash1/hash2/hash3 group which did not have a count greater than 2. If you instead want all records, with the count, then remove the HAVING clause.
As a side note, in databases which support analytic functions, such as SQL Server and Oracle, we could write a much less verbose query using COUNT as an analytic function. At some point, mainstream versions of MySQL will also support this. But for now, we are stuck with doing a join.